Title: | Statistical Process Control -- Calculation of ARL and Other Control Chart Performance Measures |
---|---|
Description: | Evaluation of control charts by means of the zero-state, steady-state ARL (Average Run Length) and RL quantiles. Setting up control charts for given in-control ARL. The control charts under consideration are one- and two-sided EWMA, CUSUM, and Shiryaev-Roberts schemes for monitoring the mean or variance of normally distributed independent data. ARL calculation of the same set of schemes under drift (in the mean) are added. Eventually, all ARL measures for the multivariate EWMA (MEWMA) are provided. |
Authors: | Sven Knoth [aut, cre] |
Maintainer: | Sven Knoth <[email protected]> |
License: | GPL (>= 2) |
Version: | 0.7.1 |
Built: | 2024-11-21 05:20:11 UTC |
Source: | https://github.com/cran/spc |
Density, distribution function and quantile function
for the sample percent defective calculated on normal samples
with mean equal to mu
and standard deviation equal to sigma
.
dphat(x, n, mu=0, sigma=1, type="known", LSL=-3, USL=3, nodes=30) pphat(q, n, mu=0, sigma=1, type="known", LSL=-3, USL=3, nodes=30) qphat(p, n, mu=0, sigma=1, type="known", LSL=-3, USL=3, nodes=30)
dphat(x, n, mu=0, sigma=1, type="known", LSL=-3, USL=3, nodes=30) pphat(q, n, mu=0, sigma=1, type="known", LSL=-3, USL=3, nodes=30) qphat(p, n, mu=0, sigma=1, type="known", LSL=-3, USL=3, nodes=30)
x , q
|
vector of quantiles. |
p |
vector of probabilities. |
n |
sample size. |
mu , sigma
|
parameters of the underlying normal distribution. |
type |
choose whether the standard deviation is given and fixed ( |
LSL , USL
|
lower and upper specification limit, respectively. |
nodes |
number of quadrature nodes needed for |
Bruhn-Suhr/Krumbholz (1990) derived the cumulative distribution function
of the sample percent defective calculated on normal samples to applying them for a new variables sampling plan.
These results were heavily used in Krumbholz/Zöller (1995) for Shewhart and in Knoth/Steinmetz (2013) for EWMA control charts.
For algorithmic details see, essentially, Bruhn-Suhr/Krumbholz (1990).
Two design variants are treated: The simple case, type="known"
, with known normal variance and the presumably much
more relevant and considerably intricate case, type="estimated"
, where both parameters of
the normal distribution are unknown. Basically, given lower and upper specification limits and the normal distribution,
one estimates the expected yield based on a normal sample of size n
.
Returns vector of pdf, cdf or qf values for the statistic phat.
Sven Knoth
M. Bruhn-Suhr and W. Krumbholz (1990), A new variables sampling plan for normally distributed lots with unknown standard deviation and double specification limits, Statistical Papers 31(1), 195-207.
W. Krumbholz and A. Zöller (1995),
p
-Karten vom Shewhartschen Typ für die messende Prüfung,
Allgemeines Statistisches Archiv 79, 347-360.
S. Knoth and S. Steinmetz (2013),
EWMA p
charts under sampling by variables,
International Journal of Production Research 51(13), 3795-3807.
phat.ewma.arl
for routines using the herewith considered phat statistic.
# Figures 1 (c) and (d) from Knoth/Steinmetz (2013) n <- 5 LSL <- -3 USL <- 3 par(mar=c(5, 5, 1, 1) + 0.1) p.star <- 2*pnorm( (LSL-USL)/2 ) # for p <= p.star pdf and cdf vanish p_ <- seq(p.star+1e-10, 0.07, 0.0001) # define support of Figure 1 # Figure 1 (c) pp_ <- pphat(p_, n) plot(p_, pp_, type="l", xlab="p", ylab=expression(P( hat(p) <= p )), xlim=c(0, 0.06), ylim=c(0,1), lwd=2) abline(h=0:1, v=p.star, col="grey") # Figure 1 (d) dp_ <- dphat(p_, n) plot(p_, dp_, type="l", xlab="p", ylab="f(p)", xlim=c(0, 0.06), ylim=c(0,50), lwd=2) abline(h=0, v=p.star, col="grey")
# Figures 1 (c) and (d) from Knoth/Steinmetz (2013) n <- 5 LSL <- -3 USL <- 3 par(mar=c(5, 5, 1, 1) + 0.1) p.star <- 2*pnorm( (LSL-USL)/2 ) # for p <= p.star pdf and cdf vanish p_ <- seq(p.star+1e-10, 0.07, 0.0001) # define support of Figure 1 # Figure 1 (c) pp_ <- pphat(p_, n) plot(p_, pp_, type="l", xlab="p", ylab=expression(P( hat(p) <= p )), xlim=c(0, 0.06), ylim=c(0,1), lwd=2) abline(h=0:1, v=p.star, col="grey") # Figure 1 (d) dp_ <- dphat(p_, n) plot(p_, dp_, type="l", xlab="p", ylab="f(p)", xlim=c(0, 0.06), ylim=c(0,50), lwd=2) abline(h=0, v=p.star, col="grey")
Computation of the (zero-state) Average Run Length (ARL) at given Poisson mean mu
.
euklid.ewma.arl(gX, gY, kL, kU, mu, y0, r0=0)
euklid.ewma.arl(gX, gY, kL, kU, mu, y0, r0=0)
gX |
first and |
gY |
second integer forming the rational lambda = gX/(gX+gY), lambda mimics the usual EWMA smoothing constant. |
kL |
lower control limit of the NCS-EWMA control chart, integer. |
kU |
upper control limit of the NCS-EWMA control chart, integer. |
mu |
mean value of Poisson distribution. |
y0 |
headstart like value – it is proposed to use the in-control mean. |
r0 |
further element of the headstart – deviating from the default should be done only in case of full understanding of the scheme. |
A new idea of applying EWMA smoothing to count data based on integer divison with remainders. It is highly recommended to read the corresponding paper (see below).
Return single value which resemble the ARL.
Sven Knoth
A. C. Rakitzis, P. Castagliola, P. E. Maravelakis (2015), A new memory-type monitoring technique for count data, Computers and Industrial Engineering 85, 235-247.
later.
# RCM (2015), Table 12, page 243, first NCS column gX <- 5 gY <- 24 kL <- 16 kU <- 24 mu0 <- 20 #L0 <- euklid.ewma.arl(gX, gY, kL, kU, mu0, mu0) # should be 1219.2
# RCM (2015), Table 12, page 243, first NCS column gX <- 5 gY <- 24 kL <- 16 kU <- 24 mu0 <- 20 #L0 <- euklid.ewma.arl(gX, gY, kL, kU, mu0, mu0) # should be 1219.2
Computation of the (zero-state) Average Run Length (ARL) at given mean mu
and sigma
etc.
imr.arl(M, Ru, mu, sigma, vsided="upper", Rl=0, cmode="coll", N=30, qm=30) imr.Ru_Mgiven(M, L0, N=30, qm=30) imr.Rl_Mgiven(M, L0, N=30, qm=30) imr.MandRu(L0, N=30, qm=30) imr.MandRuRl(L0, N=30, qm=30)
imr.arl(M, Ru, mu, sigma, vsided="upper", Rl=0, cmode="coll", N=30, qm=30) imr.Ru_Mgiven(M, L0, N=30, qm=30) imr.Rl_Mgiven(M, L0, N=30, qm=30) imr.MandRu(L0, N=30, qm=30) imr.MandRuRl(L0, N=30, qm=30)
M |
control limit multiple for mean chart. |
Ru |
upper control limit multiple for moving range chart. |
mu |
actual mean. |
sigma |
actual standard deviation. |
vsided |
switches between the more common "upper" and the less popular "two"(-sided) case of the MR chart.
Setting |
Rl |
lower control limit multiple for moving range chart (not needed in the upper case, i.e. if |
cmode |
selects the numerical algorithm. The default |
N |
Controls the dimension of the linear equation system and consequently the accuracy of the result. See details. |
qm |
Number of quadrature nodes (and weights) to determine the collocation definite integrals. |
L0 |
pre-defined in-control ARL, that is, determine |
Crowder (1987a) provided some math to determine the ARL of the so-called individual moving range (IMR) chart.
The given integral equation was approximated by a linear equation system applying trapezoidal quadratures.
Interestingly, Crowder did not recognize the specific behavior of the solution for Ru
>= M
(which is
the more common case), where the resulting function L() is constant in the central part of the
considered domain. In addition, by performing collocation on two (Ru
> M
)
or three (Ru
< M
) subintervals piecewise, one obtains highly accurate
ARL numbers. Note that imr.MandRu
yields M
and Ru
for the upper MR trace, whereas
imr.MandRuRl
provides in addition the lower factor Rl
for IMR consisting of two two-sided control charts.
Note that the underlying ARL unbiased condition suppresses the upper limit Ru
in all considered cases so far.
This is not completely surprising, because the mean chart is already quite sensitive for increases in the variance.
The two functions imr.Ru_Mgiven
and imr.Rl_Mgiven
deliver the single upper and lower limit,
respectively, if a one-sided MR design is utilized and the control lmit factor M
of
the mean chart is set already. Note that for Ru
> 2*M
, the upper MR limit is
not operative anymore. If it was initially an upper MR chart, then it reduces to a single mean chart.
If it was originally a two-sided MR design, then it becomes a two-sided mean/lower variance chart combo.
Within the latter scheme, the mean chart signals variance increases (a well-known pattern), whereas
the MR subchart delivers only decreasing variance signals. However, these simple Shewhart charts
exhibit in all configurations week variance decreases detection behavior.
Eventually, we should note that the scientific control chart community mainly recommends to
ignore MR charts, see, for example, Vardeman and Jobe (2016), whereas standards (such as ISO), commercial
SPC software and many training manuals provide the IMR scheme with completely wrong upper limits for the MR chart.
Returns either the ARL or control limit factors (alias multiples).
Sven Knoth
S. V. Crowder (1987a) Computation of ARL for Combined Individual Measurement and Moving Range Charts, Journal of Quality Technology 19(2), 98-102.
S. V. Crowder (1987b) A Program for the Computation of ARL for Combined Individual Measurement and Moving Range Charts, Journal of Quality Technology 19(2), 103-106.
K. C. B. Roes, R. J. M. M. Does, Y. Schurink, Shewhart-Type Control Charts for Individual Observations, Journal of Quality Technology 25(3), 188-198.
S. E. Rigdon, E. N. Cruthis, C. W. Champ (1994) Design Strategies for Individuals and Moving Range Control Charts, Journal of Quality Technology 26(4), 274-287.
D. Radson, L. C. Alwan (1995) Detecting Variance Reductions Using the Moving Range, Quality Engineering 8(1), 165-178.
S. R. Adke, X. Hong (1997) A Supplementary Test Based on the Control Chart for Individuals, Journal of Quality Technology 29(1), 16-20.
R. W. Amin, R. A. Ethridge (1998) A Note on Individual and Moving Range Control Charts, Journal of Quality Technology 30(1), 70-74.
C. A. Acosta-Mejia, J. J. Pignatiello (2000) Monitoring process dispersion without subgrouping, Journal of Quality Technology 32(2), 89-102.
N. B. Marks, T. C. Krehbiel (2011) Design And Application Of Individuals And Moving Range Control Charts, Journal of Applied Business Research (JABR) 25(5), 31-40.
D. Rahardja (2014) Comparison of Individual and Moving Range Chart Combinations to Individual Charts in Terms of ARL after Designing for a Common “All OK” ARL, Journal of Modern Applied Statistical Methods 13(2), 364-378.
S. B. Vardeman, J. M. Jobe (2016) Statistical Methods for Quality Assurance, Springer, 2nd edition.
later.
## Crowder (1987b), Output Listing 1, trapezoidal quadrature (less accurate) M <- 2 Ru <- 3 mu <- seq(0, 2, by=0.25) LL <- LL2 <- rep(NA, length(mu)) for ( i in 1:length(mu) ) { LL[i] <- round( imr.arl(M, Ru, mu[i], 1), digits=4) LL2[i] <- round( imr.arl(M, Ru, mu[i], 1, cmode="Crowder", N=80), digits=4) } LL1987b <- c(18.2164, 16.3541, 12.4282, 8.7559, 6.1071, 4.3582, 3.2260, 2.4878, 1.9989) print( data.frame(mu, LL2, LL1987b, LL) ) ## Crowder (1987a), Table 1, trapezoidal quadrature (less accurate) M <- 4 Ru <- 3 mu <- seq(0, 2, by=0.25) LL <- rep(NA, length(mu)) for ( i in 1:length(mu) ) LL[i] <- round( imr.arl(M, Ru, mu[i], 1), digits=4) LL1987a <- c(34.44, 34.28, 34.07, 33.81, 33.45, 32.82, 31.50, 28.85, 24.49) print( data.frame(mu, LL1987a, LL) ) ## Rigdon, Cruthis, Champ (1994), Table 1, Monte Carlo based M <- 2.992 Ru <- 4.139 icARL <- imr.arl(M, Ru, 0, 1) icARL1994 <- 200 print( data.frame(icARL1994, icARL) ) M <- 3.268 Ru <- 4.556 icARL <- imr.arl(M, Ru, 0, 1) icARL1994 <- 500 print( data.frame(icARL1994, icARL) ) ## ..., Table 2, Monte Carlo based M <- 2.992 Ru <- 4.139 tau <- c(seq(1, 1.3, by=0.05), seq(1.4, 2, by=0.1)) LL <- rep(NA, length(tau)) for ( i in 1:length(tau) ) LL[i] <- round( imr.arl(M, Ru, 0, tau[i]), digits=2) LL1994 <- c(200.54, 132.25, 90.84, 65.66, 49.35, 38.92, 31.11, 21.35, 15.47, 12.04, 9.81, 8.21, 7.03, 6.14) print( data.frame(tau, LL1994, LL) ) ## Radson, Alwan (1995), Table 2 (Monte Carlo based), half-normal, known parameter case ## two-sided (!) MR-alone (!) chart, hence the ARL results has to be decreased by 1 ## Here: a large M (=12) is deployed to mimic Inf alpha <- 0.00915 Ru <- sqrt(2) * qnorm(1-alpha/4) Rl <- sqrt(2) * qnorm(0.5+alpha/4) k <- 1.5 - (0:7)/10 LL <- rep(NA, length(k)) for ( i in 1:length(k) ) LL[i] <- round( imr.arl(12, Ru, 0, k[i], vsided="two", Rl=Rl), digits=2) - 1 RA1995 <- c(18.61, 24.51, 34.21, 49.74, 75.08, 113.14, 150.15, 164.54) print( data.frame(k, RA1995, LL) ) ## Amin, Ethridge (1998), Table 2, column sigma/sigma_0 = 1.00 M <- 3.27 Ru <- 4.56 #M <- 3.268 #Ru <- 4.556 mu <- seq(0, 2, by=0.25) LL <- rep(NA, length(mu)) for ( i in 1:length(mu) ) LL[i] <- round( imr.arl(M, Ru, mu[i], 1), digits=1) LL1998 <- c(505.3, 427.6, 276.7, 156.2, 85.0, 46.9, 26.9, 16.1, 10.1) print( data.frame(mu, LL1998, LL) ) ## ..., column sigma/sigma_0 = 1.05 for ( i in 1:length(mu) ) LL[i] <- round( imr.arl(M, Ru, mu[i], 1.05), digits=1) LL1998 <- c(296.8, 251.6, 169.6, 101.6, 58.9, 34.5, 20.9, 13.2, 8.7) print( data.frame(mu, LL1998, LL) ) ## Acosta-Mejia, Pignatiello (2000), Table 2 ## AMP utilized Markov chain approximation ## However, the MR series is not Markovian! ## MR-alone (!) chart, hence the ARL results has to be decreased by 1 ## Here: a large M (=8) is deployed to mimic Inf Ru <- 3.93 sigma <- c(1, 1.05, 1.1, 1.15, 1.2, 1.3, 1.4, 1.5, 1.75) LL <- rep(NA, length(sigma)) for ( i in 1:length(sigma) ) LL[i] <- round( imr.arl(8, Ru, 0, sigma[i], N=30), digits=1) - 1 AMP2000 <- c(201.0, 136.8, 97.9, 73.0, 56.3, 36.4, 25.6, 19.1, 11.0) print( data.frame(sigma, AMP2000, LL) ) ## Mark, Krehbiel (2011), Table 2, deployment of Crowder (1987b), nominal ic ARL 500 M <- c(3.09, 3.20, 3.30, 3.50, 4.00) Ru <- c(6.00, 4.67, 4.53, 4.42, 4.36) LL0 <- rep(NA, length(M)) for ( i in 1:length(M) ) LL0[i] <- round( imr.arl(M[i], Ru[i], 0, 1), digits=1) print( data.frame(M, Ru, LL0) )
## Crowder (1987b), Output Listing 1, trapezoidal quadrature (less accurate) M <- 2 Ru <- 3 mu <- seq(0, 2, by=0.25) LL <- LL2 <- rep(NA, length(mu)) for ( i in 1:length(mu) ) { LL[i] <- round( imr.arl(M, Ru, mu[i], 1), digits=4) LL2[i] <- round( imr.arl(M, Ru, mu[i], 1, cmode="Crowder", N=80), digits=4) } LL1987b <- c(18.2164, 16.3541, 12.4282, 8.7559, 6.1071, 4.3582, 3.2260, 2.4878, 1.9989) print( data.frame(mu, LL2, LL1987b, LL) ) ## Crowder (1987a), Table 1, trapezoidal quadrature (less accurate) M <- 4 Ru <- 3 mu <- seq(0, 2, by=0.25) LL <- rep(NA, length(mu)) for ( i in 1:length(mu) ) LL[i] <- round( imr.arl(M, Ru, mu[i], 1), digits=4) LL1987a <- c(34.44, 34.28, 34.07, 33.81, 33.45, 32.82, 31.50, 28.85, 24.49) print( data.frame(mu, LL1987a, LL) ) ## Rigdon, Cruthis, Champ (1994), Table 1, Monte Carlo based M <- 2.992 Ru <- 4.139 icARL <- imr.arl(M, Ru, 0, 1) icARL1994 <- 200 print( data.frame(icARL1994, icARL) ) M <- 3.268 Ru <- 4.556 icARL <- imr.arl(M, Ru, 0, 1) icARL1994 <- 500 print( data.frame(icARL1994, icARL) ) ## ..., Table 2, Monte Carlo based M <- 2.992 Ru <- 4.139 tau <- c(seq(1, 1.3, by=0.05), seq(1.4, 2, by=0.1)) LL <- rep(NA, length(tau)) for ( i in 1:length(tau) ) LL[i] <- round( imr.arl(M, Ru, 0, tau[i]), digits=2) LL1994 <- c(200.54, 132.25, 90.84, 65.66, 49.35, 38.92, 31.11, 21.35, 15.47, 12.04, 9.81, 8.21, 7.03, 6.14) print( data.frame(tau, LL1994, LL) ) ## Radson, Alwan (1995), Table 2 (Monte Carlo based), half-normal, known parameter case ## two-sided (!) MR-alone (!) chart, hence the ARL results has to be decreased by 1 ## Here: a large M (=12) is deployed to mimic Inf alpha <- 0.00915 Ru <- sqrt(2) * qnorm(1-alpha/4) Rl <- sqrt(2) * qnorm(0.5+alpha/4) k <- 1.5 - (0:7)/10 LL <- rep(NA, length(k)) for ( i in 1:length(k) ) LL[i] <- round( imr.arl(12, Ru, 0, k[i], vsided="two", Rl=Rl), digits=2) - 1 RA1995 <- c(18.61, 24.51, 34.21, 49.74, 75.08, 113.14, 150.15, 164.54) print( data.frame(k, RA1995, LL) ) ## Amin, Ethridge (1998), Table 2, column sigma/sigma_0 = 1.00 M <- 3.27 Ru <- 4.56 #M <- 3.268 #Ru <- 4.556 mu <- seq(0, 2, by=0.25) LL <- rep(NA, length(mu)) for ( i in 1:length(mu) ) LL[i] <- round( imr.arl(M, Ru, mu[i], 1), digits=1) LL1998 <- c(505.3, 427.6, 276.7, 156.2, 85.0, 46.9, 26.9, 16.1, 10.1) print( data.frame(mu, LL1998, LL) ) ## ..., column sigma/sigma_0 = 1.05 for ( i in 1:length(mu) ) LL[i] <- round( imr.arl(M, Ru, mu[i], 1.05), digits=1) LL1998 <- c(296.8, 251.6, 169.6, 101.6, 58.9, 34.5, 20.9, 13.2, 8.7) print( data.frame(mu, LL1998, LL) ) ## Acosta-Mejia, Pignatiello (2000), Table 2 ## AMP utilized Markov chain approximation ## However, the MR series is not Markovian! ## MR-alone (!) chart, hence the ARL results has to be decreased by 1 ## Here: a large M (=8) is deployed to mimic Inf Ru <- 3.93 sigma <- c(1, 1.05, 1.1, 1.15, 1.2, 1.3, 1.4, 1.5, 1.75) LL <- rep(NA, length(sigma)) for ( i in 1:length(sigma) ) LL[i] <- round( imr.arl(8, Ru, 0, sigma[i], N=30), digits=1) - 1 AMP2000 <- c(201.0, 136.8, 97.9, 73.0, 56.3, 36.4, 25.6, 19.1, 11.0) print( data.frame(sigma, AMP2000, LL) ) ## Mark, Krehbiel (2011), Table 2, deployment of Crowder (1987b), nominal ic ARL 500 M <- c(3.09, 3.20, 3.30, 3.50, 4.00) Ru <- c(6.00, 4.67, 4.53, 4.42, 4.36) LL0 <- rep(NA, length(M)) for ( i in 1:length(M) ) LL0[i] <- round( imr.arl(M[i], Ru[i], 0, 1), digits=1) print( data.frame(M, Ru, LL0) )
Computation of control limits of standalone MR charts.
imr.RuRl_alone(L0, N=30, qm=30, M0=12, eps=1e-3) imr.RuRl_alone_s3(L0, N=30, qm=30, M0=12) imr.RuRl_alone_tail(L0, N=30, qm=30, M0=12) imr.Ru_Rlgiven(Rl, L0, N=30, qm=30, M0=12) imr.Rl_Rugiven(Ru, L0, N=30, qm=30, M0=12)
imr.RuRl_alone(L0, N=30, qm=30, M0=12, eps=1e-3) imr.RuRl_alone_s3(L0, N=30, qm=30, M0=12) imr.RuRl_alone_tail(L0, N=30, qm=30, M0=12) imr.Ru_Rlgiven(Rl, L0, N=30, qm=30, M0=12) imr.Rl_Rugiven(Ru, L0, N=30, qm=30, M0=12)
L0 |
pre-defined in-control ARL, that is, determine |
N |
controls the dimension of the linear equation system and consequently the accuracy of the result. See details. |
qm |
number of quadrature nodes (and weights) to determine the definite collocation integrals. |
M0 |
mimics Inf — by setting |
eps |
resolution parameter, which controls the approximation of the ARL slope at the in-control level of the monitored standard deviation. It ensures the pattern that is called ARL unbiasedness. A small value is recommended. |
Rl |
lower control limit multiple for moving range chart. |
Ru |
upper control limit multiple for moving range chart. |
Crowder (1987a) provided some math to determine the ARL of the so-called individual moving range (IMR) chart,
which consists of the mean X chart and the standard deviation MR chart.
Making the alarm threshold, M0
, huge (default value here is 12) for the X chart allows us to utilize Crowder's
setup for standalone MR charts. For details about the IMR numerics see imr.arl
.
The three different versions of imr.RuRl_alone
determine limits that form an ARL unbiased design, follow the restriction
Rl
= 1/Ru^3
and feature equal probability tails for the MR's half-normal distribution,
respectively in the order given above).
The other two functions are helper routines for imr.RuRl_alone
.
Note that the elegant approach given in Acosta-Mejia/Pignatiello (2000) is only an approximation,
because the MR series is not Markovian.
Returns control limit factors (alias multiples).
Sven Knoth
S. V. Crowder (1987a) Computation of ARL for Combined Individual Measurement and Moving Range Charts, Journal of Quality Technology 19(2), 98-102.
S. V. Crowder (1987b) A Program for the Computation of ARL for Combined Individual Measurement and Moving Range Charts, Journal of Quality Technology 19(2), 103-106.
D. Radson, L. C. Alwan (1995) Detecting Variance Reductions Using the Moving Range, Quality Engineering 8(1), 165-178.
C. A. Acosta-Mejia, J. J. Pignatiello (2000) Monitoring process dispersion without subgrouping, Journal of Quality Technology 32(2), 89-102.
later.
## Radson, Alwan (1995), Table 2 (Monte Carlo based), half-normal, known parameter case ## two-sided MR-alone chart, hence the ARL results has to be decreased by 1 ## Here: a large M0=12 (default of the functions above) is deployed to mimic Inf alpha <- 0.00915 Ru <- sqrt(2) * qnorm(1-alpha/4) Rl <- sqrt(2) * qnorm(0.5+alpha/4) M0 <- 12 ## Not run: ARL0 <- imr.arl(M0, Ru, 0, 1, vsided="two", Rl=Rl) RRR1995 <- imr.RuRl_alone_tail(ARL0) RRRs <- imr.RuRl_alone_s3(ARL0) RRR <- imr.RuRl_alone(ARL0) results <- rbind(c(Rl, Ru), RRR1995, RRRs, RRR) results ## End(Not run)
## Radson, Alwan (1995), Table 2 (Monte Carlo based), half-normal, known parameter case ## two-sided MR-alone chart, hence the ARL results has to be decreased by 1 ## Here: a large M0=12 (default of the functions above) is deployed to mimic Inf alpha <- 0.00915 Ru <- sqrt(2) * qnorm(1-alpha/4) Rl <- sqrt(2) * qnorm(0.5+alpha/4) M0 <- 12 ## Not run: ARL0 <- imr.arl(M0, Ru, 0, 1, vsided="two", Rl=Rl) RRR1995 <- imr.RuRl_alone_tail(ARL0) RRRs <- imr.RuRl_alone_s3(ARL0) RRR <- imr.RuRl_alone(ARL0) results <- rbind(c(Rl, Ru), RRR1995, RRRs, RRR) results ## End(Not run)
control charts (variance charts)Computation of the (zero-state) Average Run Length (ARL)
for different types of EWMA control charts
(based on the log of the sample variance ) monitoring normal variance.
lns2ewma.arl(l,cl,cu,sigma,df,hs=NULL,sided="upper",r=40)
lns2ewma.arl(l,cl,cu,sigma,df,hs=NULL,sided="upper",r=40)
l |
smoothing parameter lambda of the EWMA control chart. |
cl |
lower control limit of the EWMA control chart. |
cu |
upper control limit of the EWMA control chart. |
sigma |
true standard deviation. |
df |
actual degrees of freedom, corresponds to subsample size (for known mean it is equal to the subsample size, for unknown mean it is equal to subsample size minus one. |
hs |
so-called headstart (enables fast initial response) – the default value (hs=NULL) corresponds to the in-control
mean of ln |
sided |
distinguishes between one- and two-sided two-sided EWMA- |
r |
dimension of the resulting linear equation system: the larger the better. |
lns2ewma.arl
determines the Average Run Length (ARL) by numerically
solving the related ARL integral equation by means of the Nystroem method
based on Gauss-Legendre quadrature.
Returns a single value which resembles the ARL.
Sven Knoth
S. V. Crowder and M. D. Hamilton (1992), An EWMA for monitoring a process standard deviation, Journal of Quality Technology 24, 12-21.
S. Knoth (2005),
Accurate ARL computation for EWMA- control charts,
Statistics and Computing 15, 341-352.
xewma.arl
for zero-state ARL computation of EWMA control charts for monitoring normal mean.
lns2ewma.ARL <- Vectorize("lns2ewma.arl", "sigma") ## Crowder/Hamilton (1992) ## moments of ln S^2 E_log_gamma <- function(df) log(2/df) + digamma(df/2) V_log_gamma <- function(df) trigamma(df/2) E_log_gamma_approx <- function(df) -1/df - 1/3/df^2 + 2/15/df^4 V_log_gamma_approx <- function(df) 2/df + 2/df^2 + 4/3/df^3 - 16/15/df^5 ## results from Table 3 ( upper chart with reflection at 0 = log(sigma0=1) ) ## original entries are (lambda = 0.05, K = 1.06, df=n-1=4) # sigma ARL # 1 200 # 1.1 43 # 1.2 18 # 1.3 11 # 1.4 7.6 # 1.5 6.0 # 2 3.2 df <- 4 lambda <- .05 K <- 1.06 cu <- K * sqrt( lambda/(2-lambda) * V_log_gamma_approx(df) ) sigmas <- c(1 + (0:5)/10, 2) arls <- round(lns2ewma.ARL(lambda, 0, cu, sigmas, df, hs=0, sided="upper"), digits=1) data.frame(sigmas, arls) ## Knoth (2005) ## compare with Table 3 (p. 351) lambda <- .05 df <- 4 K <- 1.05521 cu <- 1.05521 * sqrt( lambda/(2-lambda) * V_log_gamma_approx(df) ) ## upper chart with reflection at sigma0=1 in Table 4 ## original entries are # sigma ARL_0 ARL_-.267 # 1 200.0 200.0 # 1.1 43.04 41.55 # 1.2 18.10 19.92 # 1.3 10.75 13.11 # 1.4 7.63 9.93 # 1.5 5.97 8.11 # 2 3.17 4.67 M <- -0.267 cuM <- lns2ewma.crit(lambda, 200, df, cl=M, hs=M, r=60)[2] arls1 <- round(lns2ewma.ARL(lambda, 0, cu, sigmas, df, hs=0, sided="upper"), digits=2) arls2 <- round(lns2ewma.ARL(lambda, M, cuM, sigmas, df, hs=M, sided="upper", r=60), digits=2) data.frame(sigmas, arls1, arls2)
lns2ewma.ARL <- Vectorize("lns2ewma.arl", "sigma") ## Crowder/Hamilton (1992) ## moments of ln S^2 E_log_gamma <- function(df) log(2/df) + digamma(df/2) V_log_gamma <- function(df) trigamma(df/2) E_log_gamma_approx <- function(df) -1/df - 1/3/df^2 + 2/15/df^4 V_log_gamma_approx <- function(df) 2/df + 2/df^2 + 4/3/df^3 - 16/15/df^5 ## results from Table 3 ( upper chart with reflection at 0 = log(sigma0=1) ) ## original entries are (lambda = 0.05, K = 1.06, df=n-1=4) # sigma ARL # 1 200 # 1.1 43 # 1.2 18 # 1.3 11 # 1.4 7.6 # 1.5 6.0 # 2 3.2 df <- 4 lambda <- .05 K <- 1.06 cu <- K * sqrt( lambda/(2-lambda) * V_log_gamma_approx(df) ) sigmas <- c(1 + (0:5)/10, 2) arls <- round(lns2ewma.ARL(lambda, 0, cu, sigmas, df, hs=0, sided="upper"), digits=1) data.frame(sigmas, arls) ## Knoth (2005) ## compare with Table 3 (p. 351) lambda <- .05 df <- 4 K <- 1.05521 cu <- 1.05521 * sqrt( lambda/(2-lambda) * V_log_gamma_approx(df) ) ## upper chart with reflection at sigma0=1 in Table 4 ## original entries are # sigma ARL_0 ARL_-.267 # 1 200.0 200.0 # 1.1 43.04 41.55 # 1.2 18.10 19.92 # 1.3 10.75 13.11 # 1.4 7.63 9.93 # 1.5 5.97 8.11 # 2 3.17 4.67 M <- -0.267 cuM <- lns2ewma.crit(lambda, 200, df, cl=M, hs=M, r=60)[2] arls1 <- round(lns2ewma.ARL(lambda, 0, cu, sigmas, df, hs=0, sided="upper"), digits=2) arls2 <- round(lns2ewma.ARL(lambda, M, cuM, sigmas, df, hs=M, sided="upper", r=60), digits=2) data.frame(sigmas, arls1, arls2)
control charts (variance charts)Computation of the critical values (similar to alarm limits)
for different types of EWMA control charts
(based on the log of the sample variance ) monitoring normal variance.
lns2ewma.crit(l,L0,df,sigma0=1,cl=NULL,cu=NULL,hs=NULL,sided="upper",mode="fixed",r=40)
lns2ewma.crit(l,L0,df,sigma0=1,cl=NULL,cu=NULL,hs=NULL,sided="upper",mode="fixed",r=40)
l |
smoothing parameter lambda of the EWMA control chart. |
L0 |
in-control ARL. |
df |
actual degrees of freedom, corresponds to subsample size (for known mean it is equal to the subsample size, for unknown mean it is equal to subsample size minus one. |
sigma0 |
in-control standard deviation. |
cl |
deployed for |
cu |
for two-sided ( |
hs |
so-called headstart (enables fast initial response) – the default value (hs=NULL) corresponds to the
in-control mean of ln |
sided |
distinguishes between one- and two-sided two-sided EWMA- |
mode |
only deployed for |
r |
dimension of the resulting linear equation system: the larger the more accurate. |
lns2ewma.crit
determines the critical values (similar to alarm limits) for given in-control ARL L0
by applying secant rule and using lns2ewma.arl()
.
In case of sided
="two"
and mode
="unbiased"
a two-dimensional secant rule is applied that also ensures that the
maximum of the ARL function for given standard deviation is attained
at sigma0
. See Knoth (2010) and the related example.
Returns the lower and upper control limit cl
and cu
.
Sven Knoth
C. A. Acosta-Mej\'ia and J. J. Pignatiello Jr. and B. V. Rao (1999), A comparison of control charting procedures for monitoring process dispersion, IIE Transactions 31, 569-579.
S. V. Crowder and M. D. Hamilton (1992), An EWMA for monitoring a process standard deviation, Journal of Quality Technology 24, 12-21.
S. Knoth (2005),
Accurate ARL computation for EWMA- control charts,
Statistics and Computing 15, 341-352.
S. Knoth (2010), Control Charting Normal Variance – Reflections, Curiosities, and Recommendations, in Frontiers in Statistical Quality Control 9, H.-J. Lenz and P.-T. Wilrich (Eds.), Physica Verlag, Heidelberg, Germany, 3-18.
lns2ewma.arl
for calculation of ARL of EWMA ln control charts.
## Knoth (2005) ## compare with 1.05521 mentioned on page 350 third line from below L0 <- 200 lambda <- .05 df <- 4 limits <- lns2ewma.crit(lambda, L0, df, cl=0, hs=0) limits["cu"]/sqrt( lambda/(2-lambda)*(2/df+2/df^2+4/3/df^3-16/15/df^5) )
## Knoth (2005) ## compare with 1.05521 mentioned on page 350 third line from below L0 <- 200 lambda <- .05 df <- 4 limits <- lns2ewma.crit(lambda, L0, df, cl=0, hs=0) limits["cu"]/sqrt( lambda/(2-lambda)*(2/df+2/df^2+4/3/df^3-16/15/df^5) )
Computation of the (zero-state) Average Run Length (ARL) for multivariate exponentially weighted moving average (MEWMA) charts monitoring multivariate normal mean.
mewma.arl(l, cE, p, delta=0, hs=0, r=20, ntype=NULL, qm0=20, qm1=qm0) mewma.arl.f(l, cE, p, delta=0, r=20, ntype=NULL, qm0=20, qm1=qm0) mewma.ad(l, cE, p, delta=0, r=20, n=20, type="cond", hs=0, ntype=NULL, qm0=20, qm1=qm0)
mewma.arl(l, cE, p, delta=0, hs=0, r=20, ntype=NULL, qm0=20, qm1=qm0) mewma.arl.f(l, cE, p, delta=0, r=20, ntype=NULL, qm0=20, qm1=qm0) mewma.ad(l, cE, p, delta=0, r=20, n=20, type="cond", hs=0, ntype=NULL, qm0=20, qm1=qm0)
l |
smoothing parameter lambda of the MEWMA control chart. |
cE |
alarm threshold of the MEWMA control chart. |
p |
dimension of multivariate normal distribution. |
delta |
magnitude of the potential change, |
hs |
so-called headstart (enables fast initial response) – must be non-negative. |
r |
number of quadrature nodes – dimension of the resulting linear equation system
for |
ntype |
choose the numerical algorithm to solve the ARL integral equation. For |
type |
switch between |
n |
number of quadrature nodes for Calculating the steady-state ARL integral(s). |
qm0 , qm1
|
number of collocation quadrature nodes for the out-of-control case ( |
Basically, this is the implementation of different numerical algorithms for
solving the integral equation for the MEWMA in-control (delta
= 0) ARL introduced in Rigdon (1995a)
and out-of-control (delta
!= 0) ARL in Rigdon (1995b).
Most of them are nothing else than the Nystroem approach – the integral is replaced by a suitable quadrature.
Here, the Gauss-Legendre (more powerful), Radau (used by Rigdon, 1995a), Clenshaw-Curtis, and
Simpson rule (which is really bad) are provided.
Additionally, the collocation approach is offered as well, because it is much better for small odd values for p
.
FORTRAN code for the Radau quadrature based Nystroem of Rigdon (1995a)
was published in Bodden and Rigdon (1999) – see also https://lib.stat.cmu.edu/jqt/31-1.
Furthermore, FORTRAN code for the Markov chain approximation (in- and out-ot-control)
could be found at https://lib.stat.cmu.edu/jqt/33-4/.
The related papers are Runger and Prabhu (1996) and Molnau et al. (2001).
The idea of the Clenshaw-Curtis quadrature was taken from
Capizzi and Masarotto (2010), who successfully deployed a modified Clenshaw-Curtis quadrature
to calculate the ARL of combined (univariate) Shewhart-EWMA charts. It turns out that it works also nicely for the
MEWMA ARL. The version mewma.arl.f()
without the argument hs
provides the ARL as function of one (in-control)
or two (out-of-control) arguments.
Returns a single value which is simply the zero-state ARL.
Sven Knoth
Kevin M. Bodden and Steven E. Rigdon (1999), A program for approximating the in-control ARL for the MEWMA chart, Journal of Quality Technology 31(1), 120-123.
Giovanna Capizzi and Guido Masarotto (2010), Evaluation of the run-length distribution for a combined Shewhart-EWMA control chart, Statistics and Computing 20(1), 23-33.
Sven Knoth (2017), ARL Numerics for MEWMA Charts, Journal of Quality Technology 49(1), 78-89.
Wade E. Molnau et al. (2001), A Program for ARL Calculation for Multivariate EWMA Charts, Journal of Quality Technology 33(4), 515-521.
Sharad S. Prabhu and George C. Runger (1997), Designing a multivariate EWMA control chart, Journal of Quality Technology 29(1), 8-15.
Steven E. Rigdon (1995a), An integral equation for the in-control average run length of a multivariate exponentially weighted moving average control chart, J. Stat. Comput. Simulation 52(4), 351-365.
Steven E. Rigdon (1995b), A double-integral equation for the average run length of a multivariate exponentially weighted moving average control chart, Stat. Probab. Lett. 24(4), 365-373.
George C. Runger and Sharad S. Prabhu (1996), A Markov Chain Model for the Multivariate Exponentially Weighted Moving Averages Control Chart, J. Amer. Statist. Assoc. 91(436), 1701-1706.
mewma.crit
for getting the alarm threshold to attain a certain in-control ARL.
# Rigdon (1995a), p. 357, Tab. 1 p <- 2 r <- 0.25 h4 <- c(8.37, 9.90, 11.89, 13.36, 14.82, 16.72) for ( i in 1:length(h4) ) cat(paste(h4[i], "\t", round(mewma.arl(r, h4[i], p, ntype="ra")), "\n")) r <- 0.1 h4 <- c(6.98, 8.63, 10.77, 12.37, 13.88, 15.88) for ( i in 1:length(h4) ) cat(paste(h4[i], "\t", round(mewma.arl(r, h4[i], p, ntype="ra")), "\n")) # Rigdon (1995b), p. 372, Tab. 1 ## Not run: r <- 0.1 p <- 4 h <- 12.73 for ( sdelta in c(0, 0.125, 0.25, .5, 1, 2, 3) ) cat(paste(sdelta, "\t", round(mewma.arl(r, h, p, delta=sdelta^2, ntype="ra", r=25), digits=2), "\n")) p <- 5 h <- 14.56 for ( sdelta in c(0, 0.125, 0.25, .5, 1, 2, 3) ) cat(paste(sdelta, "\t", round(mewma.arl(r, h, p, delta=sdelta^2, ntype="ra", r=25), digits=2), "\n")) p <- 10 h <- 22.67 for ( sdelta in c(0, 0.125, 0.25, .5, 1, 2, 3) ) cat(paste(sdelta, "\t", round(mewma.arl(r, h, p, delta=sdelta^2, ntype="ra", r=25), digits=2), "\n")) ## End(Not run) # Runger/Prabhu (1996), p. 1704, Tab. 1 ## Not run: r <- 0.1 p <- 4 H <- 12.73 cat(paste(0, "\t", round(mewma.arl(r, H, p, delta=0, ntype="mc", r=50), digits=2), "\n")) for ( delta in c(.5, 1, 1.5, 2, 3) ) cat(paste(delta, "\t", round(mewma.arl(r, H, p, delta=delta, ntype="mc", r=25), digits=2), "\n")) # compare with Fortran program (MEWMA-ARLs.f90) from Molnau et al. (2001) with m1 = m2 = 25 # H4 P R DEL ARL # 12.73 4. 0.10 0.00 199.78 # 12.73 4. 0.10 0.50 35.05 # 12.73 4. 0.10 1.00 12.17 # 12.73 4. 0.10 1.50 7.22 # 12.73 4. 0.10 2.00 5.19 # 12.73 4. 0.10 3.00 3.42 p <- 20 H <- 37.01 cat(paste(0, "\t", round(mewma.arl(r, H, p, delta=0, ntype="mc", r=50), digits=2), "\n")) for ( delta in c(.5, 1, 1.5, 2, 3) ) cat(paste(delta, "\t", round(mewma.arl(r, H, p, delta=delta, ntype="mc", r=25), digits=2), "\n")) # compare with Fortran program (MEWMA-ARLs.f90) from Molnau et al. (2001) with m1 = m2 = 25 # H4 P R DEL ARL # 37.01 20. 0.10 0.00 199.09 # 37.01 20. 0.10 0.50 61.62 # 37.01 20. 0.10 1.00 20.17 # 37.01 20. 0.10 1.50 11.40 # 37.01 20. 0.10 2.00 8.03 # 37.01 20. 0.10 3.00 5.18 ## End(Not run) # Knoth (2017), p. 85, Tab. 3, rows with p=3 ## Not run: p <- 3 lambda <- 0.05 h4 <- mewma.crit(lambda, 200, p) benchmark <- mewma.arl(lambda, h4, p, delta=1, r=50) mc.arl <- mewma.arl(lambda, h4, p, delta=1, r=25, ntype="mc") ra.arl <- mewma.arl(lambda, h4, p, delta=1, r=27, ntype="ra") co.arl <- mewma.arl(lambda, h4, p, delta=1, r=12, ntype="co2") gl3.arl <- mewma.arl(lambda, h4, p, delta=1, r=30, ntype="gl3") gl5.arl <- mewma.arl(lambda, h4, p, delta=1, r=25, ntype="gl5") abs( benchmark - data.frame(mc.arl, ra.arl, co.arl, gl3.arl, gl5.arl) ) ## End(Not run) # Prabhu/Runger (1997), p. 13, Tab. 3 ## Not run: p <- 2 r <- 0.1 H <- 8.64 cat(paste(0, "\t", round(mewma.ad(r, H, p, delta=0, type="cycl", ntype="mc", r=60), digits=2), "\n")) for ( delta in c(.5, 1, 1.5, 2, 3) ) cat(paste(delta, "\t", round(mewma.ad(r, H, p, delta=delta, type="cycl", ntype="mc", r=30), digits=2), "\n")) # better accuracy for ( delta in c(0, .5, 1, 1.5, 2, 3) ) cat(paste(delta, "\t", round(mewma.ad(r, H, p, delta=delta^2, type="cycl", r=30), digits=2), "\n")) ## End(Not run)
# Rigdon (1995a), p. 357, Tab. 1 p <- 2 r <- 0.25 h4 <- c(8.37, 9.90, 11.89, 13.36, 14.82, 16.72) for ( i in 1:length(h4) ) cat(paste(h4[i], "\t", round(mewma.arl(r, h4[i], p, ntype="ra")), "\n")) r <- 0.1 h4 <- c(6.98, 8.63, 10.77, 12.37, 13.88, 15.88) for ( i in 1:length(h4) ) cat(paste(h4[i], "\t", round(mewma.arl(r, h4[i], p, ntype="ra")), "\n")) # Rigdon (1995b), p. 372, Tab. 1 ## Not run: r <- 0.1 p <- 4 h <- 12.73 for ( sdelta in c(0, 0.125, 0.25, .5, 1, 2, 3) ) cat(paste(sdelta, "\t", round(mewma.arl(r, h, p, delta=sdelta^2, ntype="ra", r=25), digits=2), "\n")) p <- 5 h <- 14.56 for ( sdelta in c(0, 0.125, 0.25, .5, 1, 2, 3) ) cat(paste(sdelta, "\t", round(mewma.arl(r, h, p, delta=sdelta^2, ntype="ra", r=25), digits=2), "\n")) p <- 10 h <- 22.67 for ( sdelta in c(0, 0.125, 0.25, .5, 1, 2, 3) ) cat(paste(sdelta, "\t", round(mewma.arl(r, h, p, delta=sdelta^2, ntype="ra", r=25), digits=2), "\n")) ## End(Not run) # Runger/Prabhu (1996), p. 1704, Tab. 1 ## Not run: r <- 0.1 p <- 4 H <- 12.73 cat(paste(0, "\t", round(mewma.arl(r, H, p, delta=0, ntype="mc", r=50), digits=2), "\n")) for ( delta in c(.5, 1, 1.5, 2, 3) ) cat(paste(delta, "\t", round(mewma.arl(r, H, p, delta=delta, ntype="mc", r=25), digits=2), "\n")) # compare with Fortran program (MEWMA-ARLs.f90) from Molnau et al. (2001) with m1 = m2 = 25 # H4 P R DEL ARL # 12.73 4. 0.10 0.00 199.78 # 12.73 4. 0.10 0.50 35.05 # 12.73 4. 0.10 1.00 12.17 # 12.73 4. 0.10 1.50 7.22 # 12.73 4. 0.10 2.00 5.19 # 12.73 4. 0.10 3.00 3.42 p <- 20 H <- 37.01 cat(paste(0, "\t", round(mewma.arl(r, H, p, delta=0, ntype="mc", r=50), digits=2), "\n")) for ( delta in c(.5, 1, 1.5, 2, 3) ) cat(paste(delta, "\t", round(mewma.arl(r, H, p, delta=delta, ntype="mc", r=25), digits=2), "\n")) # compare with Fortran program (MEWMA-ARLs.f90) from Molnau et al. (2001) with m1 = m2 = 25 # H4 P R DEL ARL # 37.01 20. 0.10 0.00 199.09 # 37.01 20. 0.10 0.50 61.62 # 37.01 20. 0.10 1.00 20.17 # 37.01 20. 0.10 1.50 11.40 # 37.01 20. 0.10 2.00 8.03 # 37.01 20. 0.10 3.00 5.18 ## End(Not run) # Knoth (2017), p. 85, Tab. 3, rows with p=3 ## Not run: p <- 3 lambda <- 0.05 h4 <- mewma.crit(lambda, 200, p) benchmark <- mewma.arl(lambda, h4, p, delta=1, r=50) mc.arl <- mewma.arl(lambda, h4, p, delta=1, r=25, ntype="mc") ra.arl <- mewma.arl(lambda, h4, p, delta=1, r=27, ntype="ra") co.arl <- mewma.arl(lambda, h4, p, delta=1, r=12, ntype="co2") gl3.arl <- mewma.arl(lambda, h4, p, delta=1, r=30, ntype="gl3") gl5.arl <- mewma.arl(lambda, h4, p, delta=1, r=25, ntype="gl5") abs( benchmark - data.frame(mc.arl, ra.arl, co.arl, gl3.arl, gl5.arl) ) ## End(Not run) # Prabhu/Runger (1997), p. 13, Tab. 3 ## Not run: p <- 2 r <- 0.1 H <- 8.64 cat(paste(0, "\t", round(mewma.ad(r, H, p, delta=0, type="cycl", ntype="mc", r=60), digits=2), "\n")) for ( delta in c(.5, 1, 1.5, 2, 3) ) cat(paste(delta, "\t", round(mewma.ad(r, H, p, delta=delta, type="cycl", ntype="mc", r=30), digits=2), "\n")) # better accuracy for ( delta in c(0, .5, 1, 1.5, 2, 3) ) cat(paste(delta, "\t", round(mewma.ad(r, H, p, delta=delta^2, type="cycl", r=30), digits=2), "\n")) ## End(Not run)
Computation of the alarm threshold for multivariate exponentially weighted moving average (MEWMA) charts monitoring multivariate normal mean.
mewma.crit(l, L0, p, hs=0, r=20)
mewma.crit(l, L0, p, hs=0, r=20)
l |
smoothing parameter lambda of the MEWMA control chart. |
L0 |
in-control ARL. |
p |
dimension of multivariate normal distribution. |
hs |
so-called headstart (enables fast initial response) – must be non-negative. |
r |
number of quadrature nodes – dimension of the resulting linear equation system. |
mewma.crit
determines the alarm threshold of for given in-control ARL L0
by applying secant rule and using mewma.arl()
with ntype="gl2"
.
Returns a single value which resembles the critical value c
.
Sven Knoth
Sven Knoth (2017), ARL Numerics for MEWMA Charts, Journal of Quality Technology 49(1), 78-89.
Steven E. Rigdon (1995), An integral equation for the in-control average run length of a multivariate exponentially weighted moving average control chart, J. Stat. Comput. Simulation 52(4), 351-365.
mewma.arl
for zero-state ARL computation.
# Rigdon (1995), p. 358, Tab. 1 p <- 4 L0 <- 500 r <- .25 h4 <- mewma.crit(r, L0, p) h4 ## original value is 16.38. # Knoth (2017), p. 82, Tab. 2 p <- 3 L0 <- 1e3 lambda <- c(0.25, 0.2, 0.15, 0.1, 0.05) h4 <- rep(NA, length(lambda) ) for ( i in 1:length(lambda) ) h4[i] <- mewma.crit(lambda[i], L0, p, r=20) round(h4, digits=2) ## original values are ## 15.82 15.62 15.31 14.76 13.60
# Rigdon (1995), p. 358, Tab. 1 p <- 4 L0 <- 500 r <- .25 h4 <- mewma.crit(r, L0, p) h4 ## original value is 16.38. # Knoth (2017), p. 82, Tab. 2 p <- 3 L0 <- 1e3 lambda <- c(0.25, 0.2, 0.15, 0.1, 0.05) h4 <- rep(NA, length(lambda) ) for ( i in 1:length(lambda) ) h4[i] <- mewma.crit(lambda[i], L0, p, r=20) round(h4, digits=2) ## original values are ## 15.82 15.62 15.31 14.76 13.60
Computation of the (zero-state) steady-state density function of the statistic deployed in multivariate exponentially weighted moving average (MEWMA) charts monitoring multivariate normal mean.
mewma.psi(l, cE, p, type="cond", hs=0, r=20)
mewma.psi(l, cE, p, type="cond", hs=0, r=20)
l |
smoothing parameter lambda of the MEWMA control chart. |
cE |
alarm threshold of the MEWMA control chart. |
p |
dimension of multivariate normal distribution. |
type |
switch between |
hs |
the re-starting point for the cyclical steady-state framework. |
r |
number of quadrature nodes. |
Basically, ideas from Knoth (2017, MEWMA numerics) and Knoth (2016, steady-state ARL concepts) are merged. More details will follow.
Returns a function.
Sven Knoth
Sven Knoth (2016), The Case Against the Use of Synthetic Control Charts, Journal of Quality Technology 48(2), 178-195.
Sven Knoth (2017), ARL Numerics for MEWMA Charts, Journal of Quality Technology 49(1), 78-89.
Sven Knoth (2018), The Steady-State Behavior of Multivariate Exponentially Weighted Moving Average Control Charts, Sequential Analysis 37(4), 511-529.
mewma.arl
for calculating the in-control ARL of MEWMA.
lambda <- 0.1 L0 <- 200 p <- 3 h4 <- mewma.crit(lambda, L0, p) x_ <- seq(0, h4*lambda/(2-lambda), by=0.002) psi <- mewma.psi(lambda, h4, p) psi_ <- psi(x_) # plot(x_, psi_, type="l", xlab="x", ylab=expression(psi(x)), xlim=c(0,1.2)) # cf. to Figure 1 in Knoth (2018), p. 514, p=3
lambda <- 0.1 L0 <- 200 p <- 3 h4 <- mewma.crit(lambda, L0, p) x_ <- seq(0, h4*lambda/(2-lambda), by=0.002) psi <- mewma.psi(lambda, h4, p) psi_ <- psi(x_) # plot(x_, psi_, type="l", xlab="x", ylab=expression(psi(x)), xlim=c(0,1.2)) # cf. to Figure 1 in Knoth (2018), p. 514, p=3
Computation of the (zero-state) Average Run Length (ARL) at given rate p
.
p.ewma.arl(lambda, ucl, n, p, z0, sided="upper", lcl=NULL, d.res=1, r.mode="ieee.round", i.mode="integer")
p.ewma.arl(lambda, ucl, n, p, z0, sided="upper", lcl=NULL, d.res=1, r.mode="ieee.round", i.mode="integer")
lambda |
smoothing parameter of the EWMA p control chart. |
ucl |
upper control limit of the EWMA p control chart. |
n |
subgroup size. |
p |
(failure/success) rate. |
z0 |
so-called headstart (give fast initial response). |
sided |
distinguishes between one- and two-sided EWMA control chart by choosing |
lcl |
lower control limit of the EWMA p control chart; needed for two-sided design. |
d.res |
resolution (see details). |
r.mode |
round mode – allowed modes are |
i.mode |
type of interval center – |
The monitored data follow a binomial distribution with size n
and failure/success probability p
.
The ARL values of the resulting EWMA control chart are determined by Markov chain approximation.
Here, the original EWMA values are approximated by
multiples of one over d.res
. Different ways of rounding (see r.mode
) to the next multiple are implemented.
Besides Gan's paper nothing is published about the numerical subtleties.
Return single value which resemble the ARL.
Sven Knoth
F. F. Gan (1990), Monitoring observations generated from a binomial distribution using modified exponentially weighted moving average control chart, J. Stat. Comput. Simulation 37, 45-60.
S. Knoth and S. Steinmetz (2013),
EWMA p
charts under sampling by variables,
International Journal of Production Research 51, 3795-3807.
later.
## Gan (1990) # Table 1 n <- 150 p0 <- .1 z0 <- n*p0 lambda <- c(1, .51, .165) hu <- c(27, 22, 18) p.value <- .1 + (0:20)/200 p.EWMA.arl <- Vectorize(p.ewma.arl, "p") arl1.value <- round(p.EWMA.arl(lambda[1], hu[1], n, p.value, z0, r.mode="round"), digits=2) arl2.value <- round(p.EWMA.arl(lambda[2], hu[2], n, p.value, z0, r.mode="round"), digits=2) arl3.value <- round(p.EWMA.arl(lambda[3], hu[3], n, p.value, z0, r.mode="round"), digits=2) arls <- matrix(c(arl1.value, arl2.value, arl3.value), ncol=length(lambda)) rownames(arls) <- p.value colnames(arls) <- paste("lambda =", lambda) arls ## Knoth/Steinmetz (2013) n <- 5 p0 <- 0.02 z0 <- n*p0 lambda <- 0.3 ucl <- 0.649169922 ## in-control ARL 370.4 (determined with d.res = 2^14 = 16384) res.list <- 2^(1:11) arl.list <- NULL for ( res in res.list ) { arl <- p.ewma.arl(lambda, ucl, n, p0, z0, d.res=res) arl.list <- c(arl.list, arl) } cbind(res.list, arl.list)
## Gan (1990) # Table 1 n <- 150 p0 <- .1 z0 <- n*p0 lambda <- c(1, .51, .165) hu <- c(27, 22, 18) p.value <- .1 + (0:20)/200 p.EWMA.arl <- Vectorize(p.ewma.arl, "p") arl1.value <- round(p.EWMA.arl(lambda[1], hu[1], n, p.value, z0, r.mode="round"), digits=2) arl2.value <- round(p.EWMA.arl(lambda[2], hu[2], n, p.value, z0, r.mode="round"), digits=2) arl3.value <- round(p.EWMA.arl(lambda[3], hu[3], n, p.value, z0, r.mode="round"), digits=2) arls <- matrix(c(arl1.value, arl2.value, arl3.value), ncol=length(lambda)) rownames(arls) <- p.value colnames(arls) <- paste("lambda =", lambda) arls ## Knoth/Steinmetz (2013) n <- 5 p0 <- 0.02 z0 <- n*p0 lambda <- 0.3 ucl <- 0.649169922 ## in-control ARL 370.4 (determined with d.res = 2^14 = 16384) res.list <- 2^(1:11) arl.list <- NULL for ( res in res.list ) { arl <- p.ewma.arl(lambda, ucl, n, p0, z0, d.res=res) arl.list <- c(arl.list, arl) } cbind(res.list, arl.list)
Computation of the (zero-state) Average Run Length (ARL), upper control limit (ucl) for given in-control ARL, and lambda for minimal out-of control ARL at given shift.
phat.ewma.arl(lambda, ucl, mu, n, z0, sigma=1, type="known", LSL=-3, USL=3, N=15, qm=25, ntype="coll") phat.ewma.crit(lambda, L0, mu, n, z0, sigma=1, type="known", LSL=-3, USL=3, N=15, qm=25) phat.ewma.lambda(L0, mu, n, z0, sigma=1, type="known", max_l=1, min_l=.001, LSL=-3, USL=3, qm=25)
phat.ewma.arl(lambda, ucl, mu, n, z0, sigma=1, type="known", LSL=-3, USL=3, N=15, qm=25, ntype="coll") phat.ewma.crit(lambda, L0, mu, n, z0, sigma=1, type="known", LSL=-3, USL=3, N=15, qm=25) phat.ewma.lambda(L0, mu, n, z0, sigma=1, type="known", max_l=1, min_l=.001, LSL=-3, USL=3, qm=25)
lambda |
smoothing parameter of the EWMA control chart. |
ucl |
upper control limit of the EWMA phat control chart. |
L0 |
pre-defined in-control ARL (Average Run Length). |
mu |
true mean or mean where the ARL should be minimized (then the in-control mean is simply 0). |
n |
subgroup size. |
z0 |
so-called headstart (gives fast initial response). |
type |
choose whether the standard deviation is given and fixed ( |
sigma |
actual standard deviation of the data – the in-control value is 1. |
max_l , min_l
|
maximal and minimal value for optimal lambda search. |
LSL , USL
|
lower and upper specification limit, respectively. |
N |
size of collocation base, dimension of the resulting linear equation system is equal to |
qm |
number of nodes for collocation quadratures. |
ntype |
switch between the default method |
The three implemented functions allow to apply a new type control chart. Basically, lower and upper specification limits are given. The monitoring vehicle then is the empirical probability that an item will not follow these specification given the sequence of sample means. If the related EWMA sequence violates the control limits, then the alarm indicates a significant process deterioration. For details see the paper mentioned in the references. To be able to construct the control charts, see the first example.
Return single values which resemble the ARL, the critical value, and the optimal lambda, respectively.
Sven Knoth
S. Knoth and S. Steinmetz (2013),
EWMA p
charts under sampling by variables,
International Journal of Production Research 51, 3795-3807.
sewma.arl
for a further collocation based ARL calculation routine.
## Simple example to demonstrate the chart. # some functions h.mu <- function(mu) pnorm(LSL-mu) + pnorm(mu-USL) ewma <- function(x, lambda=0.1, z0=0) filter(lambda*x, 1-lambda, m="r", init=z0) # parameters LSL <- -3 # lower specification limit USL <- 3 # upper specification limit n <- 5 # batch size lambda <- 0.1 # EWMA smoothing parameter L0 <- 1000 # in-control Average Run Length (ARL) z0 <- h.mu(0) # start at minimal defect level ucl <- phat.ewma.crit(lambda, L0, 0, n, z0, LSL=LSL, USL=USL) # data x0 <- matrix(rnorm(50*n), ncol=5) # in-control data x1 <- matrix(rnorm(50*n, mean=0.5), ncol=5)# out-of-control data x <- rbind(x0,x1) # all data # create chart xbar <- apply(x, 1, mean) phat <- h.mu(xbar) z <- ewma(phat, lambda=lambda, z0=z0) plot(1:length(z), z, type="l", xlab="batch", ylim=c(0,.02)) abline(h=z0, col="grey", lwd=.7) abline(h=ucl, col="red") ## S. Knoth, S. Steinmetz (2013) # Table 1 lambdas <- c(.5, .25, .2, .1) L0 <- 370.4 n <- 5 LSL <- -3 USL <- 3 phat.ewma.CRIT <- Vectorize("phat.ewma.crit", "lambda") p.star <- pnorm( LSL ) + pnorm( -USL ) ## lower bound of the chart ucls <- phat.ewma.CRIT(lambdas, L0, 0, n, p.star, LSL=LSL, USL=USL) print(cbind(lambdas, ucls)) # Table 2 mus <- c((0:4)/4, 1.5, 2, 3) phat.ewma.ARL <- Vectorize("phat.ewma.arl", "mu") arls <- NULL for ( i in 1:length(lambdas) ) { arls <- cbind(arls, round(phat.ewma.ARL(lambdas[i], ucls[i], mus, n, p.star, LSL=LSL, USL=USL), digits=2)) } arls <- data.frame(arls, row.names=NULL) names(arls) <- lambdas print(arls) # Table 3 ## Not run: mus <- c(.25, .5, 1, 2) phat.ewma.LAMBDA <- Vectorize("phat.ewma.lambda", "mu") lambdas <- phat.ewma.LAMBDA(L0, mus, n, p.star, LSL=LSL, USL=USL) print(cbind(mus, lambdas)) ## End(Not run)
## Simple example to demonstrate the chart. # some functions h.mu <- function(mu) pnorm(LSL-mu) + pnorm(mu-USL) ewma <- function(x, lambda=0.1, z0=0) filter(lambda*x, 1-lambda, m="r", init=z0) # parameters LSL <- -3 # lower specification limit USL <- 3 # upper specification limit n <- 5 # batch size lambda <- 0.1 # EWMA smoothing parameter L0 <- 1000 # in-control Average Run Length (ARL) z0 <- h.mu(0) # start at minimal defect level ucl <- phat.ewma.crit(lambda, L0, 0, n, z0, LSL=LSL, USL=USL) # data x0 <- matrix(rnorm(50*n), ncol=5) # in-control data x1 <- matrix(rnorm(50*n, mean=0.5), ncol=5)# out-of-control data x <- rbind(x0,x1) # all data # create chart xbar <- apply(x, 1, mean) phat <- h.mu(xbar) z <- ewma(phat, lambda=lambda, z0=z0) plot(1:length(z), z, type="l", xlab="batch", ylim=c(0,.02)) abline(h=z0, col="grey", lwd=.7) abline(h=ucl, col="red") ## S. Knoth, S. Steinmetz (2013) # Table 1 lambdas <- c(.5, .25, .2, .1) L0 <- 370.4 n <- 5 LSL <- -3 USL <- 3 phat.ewma.CRIT <- Vectorize("phat.ewma.crit", "lambda") p.star <- pnorm( LSL ) + pnorm( -USL ) ## lower bound of the chart ucls <- phat.ewma.CRIT(lambdas, L0, 0, n, p.star, LSL=LSL, USL=USL) print(cbind(lambdas, ucls)) # Table 2 mus <- c((0:4)/4, 1.5, 2, 3) phat.ewma.ARL <- Vectorize("phat.ewma.arl", "mu") arls <- NULL for ( i in 1:length(lambdas) ) { arls <- cbind(arls, round(phat.ewma.ARL(lambdas[i], ucls[i], mus, n, p.star, LSL=LSL, USL=USL), digits=2)) } arls <- data.frame(arls, row.names=NULL) names(arls) <- lambdas print(arls) # Table 3 ## Not run: mus <- c(.25, .5, 1, 2) phat.ewma.LAMBDA <- Vectorize("phat.ewma.lambda", "mu") lambdas <- phat.ewma.LAMBDA(L0, mus, n, p.star, LSL=LSL, USL=USL) print(cbind(mus, lambdas)) ## End(Not run)
Computation of the (zero-state) Average Run Length (ARL) at given mean mu
.
pois.cusum.arl(mu, km, hm, m, i0=0, sided="upper", rando=FALSE, gamma=0, km2=0, hm2=0, m2=0, i02=0, gamma2=0)
pois.cusum.arl(mu, km, hm, m, i0=0, sided="upper", rando=FALSE, gamma=0, km2=0, hm2=0, m2=0, i02=0, gamma2=0)
mu |
actual mean. |
km |
enumerator of rational approximation of reference value |
hm |
enumerator of rational approximation of reference value |
m |
denominator of rational approximation of reference value. |
i0 |
head start value as integer multiple of |
sided |
distinguishes between different one- and two-sided CUSUM control chart by choosing
|
rando |
Switch for activating randomization in order to allow continuous ARL control. |
gamma |
Randomization probability. If the CUSUM statistic is equal to the threshold |
km2 , hm2 , m2 , i02 , gamma2
|
corresponding values of the second CUSUM chart (to building a two-sided CUSUM scheme). |
The monitored data follow a Poisson distribution with mu
.
The ARL values of the resulting EWMA control chart are determined via Markov chain calculations.
We follow the algorithm given in Lucas (1985) expanded with some arithmetic 'tricks' (e.g., by deploying
Toeplitz matrix algebra). A paper explaining it is under preparation.
Returns a single value which resembles the ARL.
Sven Knoth
J. M. Lucas (1985) Counted data CUSUM's, Technometrics 27(2), 129-144.
C. H. White and J. B. Keats (1996) ARLs and Higher-Order Run-Length Moments for the Poisson CUSUM, Journal of Quality Technology 28(3), 363-369.
C. H. White, J. B. Keats and J. Stanley (1997) Poisson CUSUM versus c chart for defect data, Quality Engineering 9(4), 673-679.
G. Rossi and L. Lampugnani and M. Marchi (1999), An approximate CUSUM procedure for surveillance of health events, Statistics in Medicine 18(16), 2111-2122.
S. W. Han, K.-L. Tsui, B. Ariyajunya, and S. B. Kim (2010), A comparison of CUSUM, EWMA, and temporal scan statistics for detection of increases in poisson rates, Quality and Reliability Engineering International 26(3), 279-289.
M. B. Perry and J. J. Pignatiello Jr. (2011) Estimating the time of step change with Poisson CUSUM and EWMA control charts, International Journal of Production Research 49(10), 2857-2871.
later.
## Lucas 1985, upper chart (Tables 2 and 3) k <- .25 h <- 10 m <- 4 km <- m * k hm <- m * h mu0 <- 1 * k ARL <- pois.cusum.arl(mu0, km, hm-1, m) # Lucas reported 438 (in Table 2, first block, row 10.0 .25 .0 ..., column 1.0 # Recall that Lucas and other trigger an alarm, if the CUSUM statistic is greater than # or equal to the alarm threshold h print(ARL) ARL <- pois.cusum.arl(mu0, km, hm-1, m, i0=round((hm-1)/2)) # Lucas reported 333 (in Table 3, first block, row 10.0 .25 .0 ..., column 1.0 print(ARL) ## Lucas 1985, lower chart (Tables 4 and 5) ARL <- pois.cusum.arl(mu0, km, hm-1, m, sided="lower") # Lucas reported 437 (in Table 4, first block, row 10.0 .25 .0 ..., column 1.0 print(ARL) ARL <- pois.cusum.arl(mu0, km, hm-1, m, i0=round((hm-1)/2), sided="lower") # Lucas reported 318 (in Table 5, first block, row 10.0 .25 .0 ..., column 1.0 print(ARL)
## Lucas 1985, upper chart (Tables 2 and 3) k <- .25 h <- 10 m <- 4 km <- m * k hm <- m * h mu0 <- 1 * k ARL <- pois.cusum.arl(mu0, km, hm-1, m) # Lucas reported 438 (in Table 2, first block, row 10.0 .25 .0 ..., column 1.0 # Recall that Lucas and other trigger an alarm, if the CUSUM statistic is greater than # or equal to the alarm threshold h print(ARL) ARL <- pois.cusum.arl(mu0, km, hm-1, m, i0=round((hm-1)/2)) # Lucas reported 333 (in Table 3, first block, row 10.0 .25 .0 ..., column 1.0 print(ARL) ## Lucas 1985, lower chart (Tables 4 and 5) ARL <- pois.cusum.arl(mu0, km, hm-1, m, sided="lower") # Lucas reported 437 (in Table 4, first block, row 10.0 .25 .0 ..., column 1.0 print(ARL) ARL <- pois.cusum.arl(mu0, km, hm-1, m, i0=round((hm-1)/2), sided="lower") # Lucas reported 318 (in Table 5, first block, row 10.0 .25 .0 ..., column 1.0 print(ARL)
Computation of the CUSUM upper limit and, if needed, of the randomization probability, given mean mu0
.
pois.cusum.crit(mu0, km, A, m, i0=0, sided="upper", rando=FALSE)
pois.cusum.crit(mu0, km, A, m, i0=0, sided="upper", rando=FALSE)
mu0 |
actual in-control mean. |
km |
enumerator of rational approximation of reference value |
A |
target in-control ARL (average run length). |
m |
denominator of rational approximation of reference value. |
i0 |
head start value as integer multiple of |
sided |
distinguishes between different one- and two-sided CUSUM control chart by choosing
|
rando |
Switch for activating randomization in order to allow continuous ARL control. |
The monitored data follow a Poisson distribution with mu
(here the in-control level mu0
).
The ARL values of the resulting EWMA control chart are determined via Markov chain calculations.
With some grid search, we obtain the smallest value for the integer threshold component hm
so that
the resulting ARL is not smaller than A
. If equality is needed, then activating rando=TRUE
yields the corresponding randomization probability gamma
.
More details will follow in a paper that will be submitted in 2020.
Returns two single values, integer threshold hm
resulting in the final
alarm threshold h=hm/m
, and the randomization probability.
Sven Knoth
J. M. Lucas (1985) Counted data CUSUM's, Technometrics 27(2), 129-144.
C. H. White and J. B. Keats (1996) ARLs and Higher-Order Run-Length Moments for the Poisson CUSUM, Journal of Quality Technology 28(3), 363-369.
C. H. White, J. B. Keats and J. Stanley (1997) Poisson CUSUM versus c chart for defect data, Quality Engineering 9(4), 673-679.
G. Rossi and L. Lampugnani and M. Marchi (1999), An approximate CUSUM procedure for surveillance of health events, Statistics in Medicine 18(16), 2111-2122.
S. W. Han, K.-L. Tsui, B. Ariyajunya, and S. B. Kim (2010), A comparison of CUSUM, EWMA, and temporal scan statistics for detection of increases in poisson rates, Quality and Reliability Engineering International 26(3), 279-289.
M. B. Perry and J. J. Pignatiello Jr. (2011) Estimating the time of step change with Poisson CUSUM and EWMA control charts, International Journal of Production Research 49(10), 2857-2871.
later.
## Lucas 1985 mu0 <- 0.25 km <- 1 A <- 430 m <- 4 #cv <- pois.cusum.crit(mu0, km, A, m) cv <- c(40, 0) # Lucas reported h = 10 alias hm = 40 (in Table 2, first block, row 10.0 .25 .0 ..., column 1.0 # Recall that Lucas and other trigger an alarm, if the CUSUM statistic is greater than # or equal to the alarm threshold h print(cv)
## Lucas 1985 mu0 <- 0.25 km <- 1 A <- 430 m <- 4 #cv <- pois.cusum.crit(mu0, km, A, m) cv <- c(40, 0) # Lucas reported h = 10 alias hm = 40 (in Table 2, first block, row 10.0 .25 .0 ..., column 1.0 # Recall that Lucas and other trigger an alarm, if the CUSUM statistic is greater than # or equal to the alarm threshold h print(cv)
Computation of the reference value k and the alarm threshold h for one-sided CUSUM control charts monitoring Poisson data, if the in-control ARL L0 and the out-of-control ARL L1 are given.
pois.cusum.crit.L0L1(mu0, L0, L1, sided="upper", OUTPUT=FALSE)
pois.cusum.crit.L0L1(mu0, L0, L1, sided="upper", OUTPUT=FALSE)
mu0 |
in-control Poisson mean. |
L0 |
in-control ARL. |
L1 |
out-of-control ARL. |
sided |
distinguishes between |
OUTPUT |
controls whether iteration details are printed. |
pois.cusum.crit.L0L1
determines the reference value k and the alarm threshold h
for given in-control ARL L0
and out-of-control ARL L1
by applying grid search and using pois.cusum.arl()
and pois.cusum.crit()
.
These CUSUM design rules were firstly (and quite rarely afterwards) used by Ewan and Kemp.
In the Poisson case, Rossi et al. applied them while analyzing three different normal
approximations of the Poisson distribution. See the example which illustrates
the validity of all these approaches.
Returns a data frame with results for the denominator m
of the rational approximation,
km
as (integer) enumerator of the reference value (approximation), the corresponding
out-of-control mean mu1
, the final approximation k
of the reference value,
the threshold values hm
(integer) and h
(=hm/m
), and the randomization constant
gamma
(the target in-control ARL is exactly matched).
Sven Knoth
W. D. Ewan and K. W. Kemp (1960), Sampling inspection of continuous processes with no autocorrelation between successive results, Biometrika 47 (3/4), 363-380.
K. W. Kemp (1962), The Use of Cumulative Sums for Sampling Inspection Schemes, Journal of the Royal Statistical Sociecty C, Applied Statistics 11(1), 16-31.
G. Rossi, L. Lampugnani and M. Marchi (1999), An approximate CUSUM procedure for surveillance of health events, Statistics in Medicine 18(16), 2111-2122.
pois.cusum.arl
for zero-state ARL and pois.cusum.crit
for threshold h computation.
## Table 1 from Rossi et al. (1999) -- one-sided CUSUM La <- 500 # in-control ARL Lr <- 7 # out-of-control ARL m_a <- 0.52 # in-control mean of the Poisson variate ## Not run: kh <- xcusum.crit.L0L1(La, Lr, sided="one") # kh <- ...: instead of deploying EK1960, one could use more accurate numbers EK_k <- 0.60 # EK1960 results in EK_h <- 3.80 # Table 2 on p. 372 eZR <- 2*EK_h # reproduce normal ooc mean from reference value k m_r <- 1.58 # EK1960 Table 3 on p. 377 for m_a = 0.52 R1 <- round( eZR/sqrt(m_a) + 1, digits=2) R2 <- round( ( eZR/2/sqrt(m_a) + 1 )^2, digits=2) R3 <- round(( sqrt(4 + 2*eZR/sqrt(m_a)) - 1 )^2, digits=2) RS <- round( m_r / m_a, digits=2 ) ## Not run: K_hk <- pois.cusum.crit.L0L1(m_a, La, Lr) # 'our' 'exact' approach K_hk <- data.frame(m=1000, km=948, mu1=1.563777, k=0.948, hm=3832, h=3.832, gamma=0.1201901) # get k for competing means mu0 (m_a) and mu1 (m_r) k_m01 <- function(mu0, mu1) (mu1 - mu0) / (log(mu1) - log(mu0)) # get ooc mean mu1 (m_r) for given mu0 (m_a) and reference value k m1_km0 <- function(mu0, k) { zero <- function(x) k - k_m01(mu0,x) upper <- mu0 + .5 while ( zero(upper) > 0 ) upper <- upper + 0.5 mu1 <- uniroot(zero, c(mu0*1.00000001, upper), tol=1e-9)$root mu1 } K_m_r <- m1_km0(m_a, K_hk$k) RK <- round( K_m_r / m_a, digits=2 ) cat(paste(m_a, R1, R2, R3, RS, RK, "\n", sep="\t"))
## Table 1 from Rossi et al. (1999) -- one-sided CUSUM La <- 500 # in-control ARL Lr <- 7 # out-of-control ARL m_a <- 0.52 # in-control mean of the Poisson variate ## Not run: kh <- xcusum.crit.L0L1(La, Lr, sided="one") # kh <- ...: instead of deploying EK1960, one could use more accurate numbers EK_k <- 0.60 # EK1960 results in EK_h <- 3.80 # Table 2 on p. 372 eZR <- 2*EK_h # reproduce normal ooc mean from reference value k m_r <- 1.58 # EK1960 Table 3 on p. 377 for m_a = 0.52 R1 <- round( eZR/sqrt(m_a) + 1, digits=2) R2 <- round( ( eZR/2/sqrt(m_a) + 1 )^2, digits=2) R3 <- round(( sqrt(4 + 2*eZR/sqrt(m_a)) - 1 )^2, digits=2) RS <- round( m_r / m_a, digits=2 ) ## Not run: K_hk <- pois.cusum.crit.L0L1(m_a, La, Lr) # 'our' 'exact' approach K_hk <- data.frame(m=1000, km=948, mu1=1.563777, k=0.948, hm=3832, h=3.832, gamma=0.1201901) # get k for competing means mu0 (m_a) and mu1 (m_r) k_m01 <- function(mu0, mu1) (mu1 - mu0) / (log(mu1) - log(mu0)) # get ooc mean mu1 (m_r) for given mu0 (m_a) and reference value k m1_km0 <- function(mu0, k) { zero <- function(x) k - k_m01(mu0,x) upper <- mu0 + .5 while ( zero(upper) > 0 ) upper <- upper + 0.5 mu1 <- uniroot(zero, c(mu0*1.00000001, upper), tol=1e-9)$root mu1 } K_m_r <- m1_km0(m_a, K_hk$k) RK <- round( K_m_r / m_a, digits=2 ) cat(paste(m_a, R1, R2, R3, RS, RK, "\n", sep="\t"))
Computation of the steady-state Average Run Length (ARL) at given mean mu
.
pois.ewma.ad(lambda, AL, AU, mu0, mu, sided="two", rando=FALSE, gL=0, gU=0, mcdesign="classic", N=101)
pois.ewma.ad(lambda, AL, AU, mu0, mu, sided="two", rando=FALSE, gL=0, gU=0, mcdesign="classic", N=101)
lambda |
smoothing parameter of the EWMA p control chart. |
AL , AU
|
factors to build the lower and upper control limit, respectively, of the Poisson EWMA control chart. |
mu0 |
in-control mean. |
mu |
actual mean. |
sided |
distinguishes between one- and two-sided EWMA control chart by choosing
|
rando |
Switch between the standard limit treatment, |
gL , gU
|
If the EWMA statistic is at the limit (approximately), then an alarm is triggered with probability
|
mcdesign |
choose either |
N |
number of states of the approximating Markov chain; is equal to the dimension of the resulting linear equation system. |
The monitored data follow a Poisson distribution with mu
.
The ARL values of the resulting EWMA control chart are determined by Markov chain approximation.
We follow the algorithm given in Borror, Champ and Rigdon (1998). The function is in an early development phase.
Return single value which resembles the steady-state ARL.
Sven Knoth
C. M. Borror, C. W. Champ and S. E. Rigdon (1998) Poisson EWMA control charts, Journal of Quality Technonlogy 30(4), 352-361.
M. C. Morais and S. Knoth (2020) Improving the ARL profile and the accuracy of its calculation for Poisson EWMA charts, Quality and Reliability Engineering International 36(3), 876-889.
later.
## Borror, Champ and Rigdon (1998), Table 2, PEWMA column mu0 <- 20 lambda <- 0.27 A <- 3.319 mu1 <- c(2*(3:15), 35) ARL1 <- AD1 <- rep(NA, length(mu1)) for ( i in 1:length(mu1) ) { ARL1[i] <- round(pois.ewma.arl(lambda,A,A,mu0,mu0,mu1[i],mcdesign="classic"),digits=1) AD1[i] <- round(pois.ewma.ad(lambda,A,A,mu0,mu1[i],mcdesign="classic"),digits=1) } print( cbind(mu1, ARL1, AD1) ) ## Morais and Knoth (2020), Table 2, lambda = 0.27 column ## randomisation not implemented for pois.ewma.ad() lambda <- 0.27 AL <- 3.0870 AU <- 3.4870 gL <- 0.001029 gU <- 0.000765 mu2 <- c(16, 18, 19.99, mu0, 20.01, 22, 24) ARL2 <- AD2 <- rep(NA, length(mu2)) for ( i in 1:length(mu2) ) { ARL2[i] <- round(pois.ewma.arl(lambda,AL,AU,mu0,mu0,mu2[i],rando=FALSE), digits=1) AD2[i] <- round(pois.ewma.ad(lambda,AL,AU,mu0,mu2[i],rando=FALSE), digits=1) } print( cbind(mu2, ARL2, AD2) )
## Borror, Champ and Rigdon (1998), Table 2, PEWMA column mu0 <- 20 lambda <- 0.27 A <- 3.319 mu1 <- c(2*(3:15), 35) ARL1 <- AD1 <- rep(NA, length(mu1)) for ( i in 1:length(mu1) ) { ARL1[i] <- round(pois.ewma.arl(lambda,A,A,mu0,mu0,mu1[i],mcdesign="classic"),digits=1) AD1[i] <- round(pois.ewma.ad(lambda,A,A,mu0,mu1[i],mcdesign="classic"),digits=1) } print( cbind(mu1, ARL1, AD1) ) ## Morais and Knoth (2020), Table 2, lambda = 0.27 column ## randomisation not implemented for pois.ewma.ad() lambda <- 0.27 AL <- 3.0870 AU <- 3.4870 gL <- 0.001029 gU <- 0.000765 mu2 <- c(16, 18, 19.99, mu0, 20.01, 22, 24) ARL2 <- AD2 <- rep(NA, length(mu2)) for ( i in 1:length(mu2) ) { ARL2[i] <- round(pois.ewma.arl(lambda,AL,AU,mu0,mu0,mu2[i],rando=FALSE), digits=1) AD2[i] <- round(pois.ewma.ad(lambda,AL,AU,mu0,mu2[i],rando=FALSE), digits=1) } print( cbind(mu2, ARL2, AD2) )
Computation of the (zero-state) Average Run Length (ARL) at given mean mu
.
pois.ewma.arl(lambda, AL, AU, mu0, z0, mu, sided="two", rando=FALSE, gL=0, gU=0, mcdesign="transfer", N=101)
pois.ewma.arl(lambda, AL, AU, mu0, z0, mu, sided="two", rando=FALSE, gL=0, gU=0, mcdesign="transfer", N=101)
lambda |
smoothing parameter of the EWMA p control chart. |
AL , AU
|
factors to build the lower and upper control limit, respectively, of the Poisson EWMA control chart. |
mu0 |
in-control mean. |
z0 |
so-called headstart (give fast initial response). |
mu |
actual mean. |
sided |
distinguishes between one- and two-sided EWMA control chart by choosing
|
rando |
Switch between the standard limit treatment, |
gL , gU
|
If the EWMA statistic is at the limit (approximately), then an alarm is triggered with probability
|
mcdesign |
choose either |
N |
number of states of the approximating Markov chain; is equal to the dimension of the resulting linear equation system. |
The monitored data follow a Poisson distribution with mu
.
The ARL values of the resulting EWMA control chart are determined by Markov chain approximation.
We follow the algorithm given in Borror, Champ and Rigdon (1998).
However, by setting mcdesign="transfer"
(now the default) from Morais and Knoth (2020),
the accuracy is considerably improved.
Return single value which resembles the ARL.
Sven Knoth
C. M. Borror, C. W. Champ and S. E. Rigdon (1998) Poisson EWMA control charts, Journal of Quality Technonlogy 30(4), 352-361.
M. C. Morais and S. Knoth (2020) Improving the ARL profile and the accuracy of its calculation for Poisson EWMA charts, Quality and Reliability Engineering International 36(3), 876-889.
later.
## Borror, Champ and Rigdon (1998), Table 2, PEWMA column mu0 <- 20 lambda <- 0.27 A <- 3.319 mu1 <- c(2*(3:15), 35) ARL1 <- rep(NA, length(mu1)) for ( i in 1:length(mu1) ) ARL1[i] <- pois.ewma.arl(lambda, A, A, mu0, mu0, mu1[i], mcdesign="classic") print(cbind(mu1, round(ARL1, digits=1))) ## the same numbers with improved accuracy ARL2 <- rep(NA, length(mu1)) for ( i in 1:length(mu1) ) ARL2[i] <- pois.ewma.arl(lambda, A, A, mu0, mu0, mu1[i], mcdesign="transfer") print(cbind(mu1, round(ARL2, digits=1))) ## Morais and Knoth (2020), Table 2, lambda = 0.27 column lambda <- 0.27 AL <- 3.0870 AU <- 3.4870 gL <- 0.001029 gU <- 0.000765 mu0 <- 20 mu1 <- c(16, 18, 19.99, mu0, 20.01, 22, 24) ARL3 <- rep(NA, length(mu1)) for ( i in 1:length(mu1) ) ARL3[i] <- pois.ewma.arl(lambda,AL,AU,mu0,mu0,mu1[i],rando=TRUE,gL=gL,gU=gU, N=101) print(cbind(mu1, round(ARL3, digits=1)))
## Borror, Champ and Rigdon (1998), Table 2, PEWMA column mu0 <- 20 lambda <- 0.27 A <- 3.319 mu1 <- c(2*(3:15), 35) ARL1 <- rep(NA, length(mu1)) for ( i in 1:length(mu1) ) ARL1[i] <- pois.ewma.arl(lambda, A, A, mu0, mu0, mu1[i], mcdesign="classic") print(cbind(mu1, round(ARL1, digits=1))) ## the same numbers with improved accuracy ARL2 <- rep(NA, length(mu1)) for ( i in 1:length(mu1) ) ARL2[i] <- pois.ewma.arl(lambda, A, A, mu0, mu0, mu1[i], mcdesign="transfer") print(cbind(mu1, round(ARL2, digits=1))) ## Morais and Knoth (2020), Table 2, lambda = 0.27 column lambda <- 0.27 AL <- 3.0870 AU <- 3.4870 gL <- 0.001029 gU <- 0.000765 mu0 <- 20 mu1 <- c(16, 18, 19.99, mu0, 20.01, 22, 24) ARL3 <- rep(NA, length(mu1)) for ( i in 1:length(mu1) ) ARL3[i] <- pois.ewma.arl(lambda,AL,AU,mu0,mu0,mu1[i],rando=TRUE,gL=gL,gU=gU, N=101) print(cbind(mu1, round(ARL3, digits=1)))
Computation of the (zero-state) Average Run Length (ARL) at given mean mu
.
pois.ewma.crit(lambda, L0, mu0, z0, AU=3, sided="two", design="sym", rando=FALSE, mcdesign="transfer", N=101, jmax=4)
pois.ewma.crit(lambda, L0, mu0, z0, AU=3, sided="two", design="sym", rando=FALSE, mcdesign="transfer", N=101, jmax=4)
lambda |
smoothing parameter of the EWMA p control chart. |
L0 |
value of the so-called in-control Average Run Length (ARL) for the Poisson EWMA control chart. |
mu0 |
in-control mean. |
z0 |
so-called headstart (give fast initial response). |
AU |
in case of the lower chart deployed as reflecting upper barrier – might be increased step by step until the resulting lower limit does not change anymore. |
sided |
distinguishes between one- and two-sided EWMA control chart by choosing |
design |
distinguishes between limits symmetric to the in-control mean |
rando |
Switch between the standard limit treatment, |
mcdesign |
choose either |
N |
number of states of the approximating Markov chain; is equal to the dimension of the resulting linear equation system. |
jmax |
number of digits for the to be calculated factors |
The monitored data follow a Poisson distribution with mu
.
Here we solve the inverse task to the usual ARL calculation. Hence, determine the control limit factors
so that the in-control ARL is (roughly) equal to L0
.
The ARL values underneath the routine are determined by Markov chain approximation.
The algorithm is just a grid search that takes care of the discrete ARL behavior.
Return one or two values being he control limit factors.
Sven Knoth
C. M. Borror, C. W. Champ and S. E. Rigdon (1998) Poisson EWMA control charts, Journal of Quality Technonlogy 30(4), 352-361.
M. C. Morais and S. Knoth (2020) Improving the ARL profile and the accuracy of its calculation for Poisson EWMA charts, Quality and Reliability Engineering International 36(3), 876-889.
later.
## Borror, Champ and Rigdon (1998), page 30, original value is A = 2.8275 mu0 <- 4 lambda <- 0.2 L0 <- 351 A <- pois.ewma.crit(lambda, L0, mu0, mu0, mcdesign="classic") print(round(A, digits=4)) ## Morais and Knoth (2020), Table 2, lambda = 0.27 column lambda <- 0.27 L0 <- 1233.4 ccgg <- pois.ewma.crit(lambda,1233.4,mu0,mu0,design="unb",rando=TRUE,mcdesign="transfer") print(ccgg, digits=3)
## Borror, Champ and Rigdon (1998), page 30, original value is A = 2.8275 mu0 <- 4 lambda <- 0.2 L0 <- 351 A <- pois.ewma.crit(lambda, L0, mu0, mu0, mcdesign="classic") print(round(A, digits=4)) ## Morais and Knoth (2020), Table 2, lambda = 0.27 column lambda <- 0.27 L0 <- 1233.4 ccgg <- pois.ewma.crit(lambda,1233.4,mu0,mu0,design="unb",rando=TRUE,mcdesign="transfer") print(ccgg, digits=3)
Computation of the nodes and weights to enable numerical quadrature.
quadrature.nodes.weights(n, type="GL", x1=-1, x2=1)
quadrature.nodes.weights(n, type="GL", x1=-1, x2=1)
n |
number of nodes (and weights). |
type |
quadrature type – currently Gauss-Legendre, |
x1 |
lower limit of the integration interval. |
x2 |
upper limit of the integration interval. |
A more detailed description will follow soon. The algorithm for the Gauss-Legendre quadrature was delivered by Knut Petras to me, while the one for the Radau quadrature was taken from John Burkardt.
Returns two vectors which hold the needed quadrature nodes and weights.
Sven Knoth
H. Brass and K. Petras (2011), Quadrature Theory. The Theory of Numerical Integration on a Compact Interval, Mathematical Surveys and Monographs, American Mathematical Society.
John Burkardt (2015), https://people.math.sc.edu/Burkardt/c_src/quadrule/quadrule.c
Many of the ARL routines use the Gauss-Legendre nodes.
# GL n <- 10 qnw <-quadrature.nodes.weights(n, type="GL") qnw # Radau n <- 10 qnw <-quadrature.nodes.weights(n, type="Ra") qnw
# GL n <- 10 qnw <-quadrature.nodes.weights(n, type="GL") qnw # Radau n <- 10 qnw <-quadrature.nodes.weights(n, type="Ra") qnw
Computation of the (zero-state) Average Run Length (ARL)
for different types of CUSUM control charts (based on the sample variance
) monitoring normal variance.
scusum.arl(k, h, sigma, df, hs=0, sided="upper", k2=NULL, h2=NULL, hs2=0, r=40, qm=30, version=2)
scusum.arl(k, h, sigma, df, hs=0, sided="upper", k2=NULL, h2=NULL, hs2=0, r=40, qm=30, version=2)
k |
reference value of the CUSUM control chart. |
h |
decision interval (alarm limit, threshold) of the CUSUM control chart. |
sigma |
true standard deviation. |
df |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided two-sided CUSUM- |
k2 |
In case of a two-sided CUSUM chart for variance the reference value of the lower chart. |
h2 |
In case of a two-sided CUSUM chart for variance the decision interval of the lower chart. |
hs2 |
In case of a two-sided CUSUM chart for variance the headstart of the lower chart. |
r |
Dimension of the resulting linear equation system (highest order of the collocation polynomials times number of intervals – see Knoth 2006). |
qm |
Number of quadrature nodes for calculating the collocation definite integrals. |
version |
Distinguish version numbers (1,2,...). For internal use only. |
scusum.arl
determines the Average Run Length (ARL) by numerically
solving the related ARL integral equation by means of collocation (piecewise Chebyshev polynomials).
Returns a single value which resembles the ARL.
Sven Knoth
S. Knoth (2005),
Accurate ARL computation for EWMA- control charts,
Statistics and Computing 15, 341-352.
S. Knoth (2006),
Computation of the ARL for CUSUM- schemes,
Computational Statistics & Data Analysis 51, 499-512.
xcusum.arl
for zero-state ARL computation of CUSUM control charts for monitoring normal mean.
## Knoth (2006) ## compare with Table 1 (p. 507) k <- 1.46 # sigma1 = 1.5 df <- 1 h <- 10 # original values # sigma coll63 BE Hawkins MC 10^9 (s.e.) # 1 260.7369 260.7546 261.32 260.7399 (0.0081) # 1.1 90.1319 90.1389 90.31 90.1319 (0.0027) # 1.2 43.6867 43.6897 43.75 43.6845 (0.0013) # 1.3 26.2916 26.2932 26.32 26.2929 (0.0007) # 1.4 18.1231 18.1239 18.14 18.1235 (0.0005) # 1.5 13.6268 13.6273 13.64 13.6272 (0.0003) # 2 5.9904 5.9910 5.99 5.9903 (0.0001) # replicate the column coll63 sigma <- c(1, 1.1, 1.2, 1.3, 1.4, 1.5, 2) arl <- rep(NA, length(sigma)) for ( i in 1:length(sigma) ) arl[i] <- round(scusum.arl(k, h, sigma[i], df, r=63, qm=20, version=2), digits=4) data.frame(sigma, arl)
## Knoth (2006) ## compare with Table 1 (p. 507) k <- 1.46 # sigma1 = 1.5 df <- 1 h <- 10 # original values # sigma coll63 BE Hawkins MC 10^9 (s.e.) # 1 260.7369 260.7546 261.32 260.7399 (0.0081) # 1.1 90.1319 90.1389 90.31 90.1319 (0.0027) # 1.2 43.6867 43.6897 43.75 43.6845 (0.0013) # 1.3 26.2916 26.2932 26.32 26.2929 (0.0007) # 1.4 18.1231 18.1239 18.14 18.1235 (0.0005) # 1.5 13.6268 13.6273 13.64 13.6272 (0.0003) # 2 5.9904 5.9910 5.99 5.9903 (0.0001) # replicate the column coll63 sigma <- c(1, 1.1, 1.2, 1.3, 1.4, 1.5, 2) arl <- rep(NA, length(sigma)) for ( i in 1:length(sigma) ) arl[i] <- round(scusum.arl(k, h, sigma[i], df, r=63, qm=20, version=2), digits=4) data.frame(sigma, arl)
omputation of the decision intervals (alarm limits)
for different types of CUSUM control charts (based on the sample
variance ) monitoring normal variance.
scusum.crit(k, L0, sigma, df, hs=0, sided="upper", mode="eq.tails", k2=NULL, hs2=0, r=40, qm=30)
scusum.crit(k, L0, sigma, df, hs=0, sided="upper", mode="eq.tails", k2=NULL, hs2=0, r=40, qm=30)
k |
reference value of the CUSUM control chart. |
L0 |
in-control ARL. |
sigma |
true standard deviation. |
df |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided two-sided CUSUM- |
mode |
only deployed for |
k2 |
in case of a two-sided CUSUM chart for variance the reference value of the lower chart. |
hs2 |
in case of a two-sided CUSUM chart for variance the headstart of the lower chart. |
r |
Dimension of the resulting linear equation system (highest order of the collocation polynomials times number of intervals – see Knoth 2006). |
qm |
Number of quadrature nodes for calculating the collocation definite integrals. |
scusum.crit
ddetermines the decision interval (alarm limit)
for given in-control ARL L0
by applying secant rule and using scusum.arl()
.
Returns a single value which resembles the decision interval h
.
Sven Knoth
S. Knoth (2005),
Accurate ARL computation for EWMA- control charts,
Statistics and Computing 15, 341-352.
S. Knoth (2006),
Computation of the ARL for CUSUM- schemes,
Computational Statistics & Data Analysis 51, 499-512.
xcusum.arl
for zero-state ARL computation of CUSUM control charts monitoring normal mean.
## Knoth (2006) ## compare with Table 1 (p. 507) k <- 1.46 # sigma1 = 1.5 df <- 1 L0 <- 260.74 h <- scusum.crit(k, L0, 1, df) h # original value is 10
## Knoth (2006) ## compare with Table 1 (p. 507) k <- 1.46 # sigma1 = 1.5 df <- 1 L0 <- 260.74 h <- scusum.crit(k, L0, 1, df) h # original value is 10
Computation of the (zero-state) Average Run Length (ARL)
for different types of CUSUM-Shewhart combo control charts (based on the sample variance
) monitoring normal variance.
scusums.arl(k, h, cS, sigma, df, hs=0, sided="upper", k2=NULL, h2=NULL, hs2=0, r=40, qm=30, version=2)
scusums.arl(k, h, cS, sigma, df, hs=0, sided="upper", k2=NULL, h2=NULL, hs2=0, r=40, qm=30, version=2)
k |
reference value of the CUSUM control chart. |
h |
decision interval (alarm limit, threshold) of the CUSUM control chart. |
cS |
Shewhart limit. |
sigma |
true standard deviation. |
df |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided two-sided CUSUM- |
k2 |
In case of a two-sided CUSUM chart for variance the reference value of the lower chart. |
h2 |
In case of a two-sided CUSUM chart for variance the decision interval of the lower chart. |
hs2 |
In case of a two-sided CUSUM chart for variance the headstart of the lower chart. |
r |
Dimension of the resulting linear equation system (highest order of the collocation polynomials times number of intervals – see Knoth 2006). |
qm |
Number of quadrature nodes for calculating the collocation definite integrals. |
version |
Distinguish version numbers (1,2,...). For internal use only. |
scusums.arl
determines the Average Run Length (ARL) by numerically
solving the related ARL integral equation by means of collocation (piecewise Chebyshev polynomials).
Returns a single value which resembles the ARL.
Sven Knoth
S. Knoth (2006),
Computation of the ARL for CUSUM- schemes,
Computational Statistics & Data Analysis 51, 499-512.
scusum.arl
for zero-state ARL computation of standalone CUSUM control charts for monitoring normal variance.
## will follow
## will follow
Computation of the (zero-state) Average Run Length (ARL)
for different types of EWMA control charts (based on the sample variance
) monitoring normal variance.
sewma.arl(l,cl,cu,sigma,df,s2.on=TRUE,hs=NULL,sided="upper",r=40,qm=30)
sewma.arl(l,cl,cu,sigma,df,s2.on=TRUE,hs=NULL,sided="upper",r=40,qm=30)
l |
smoothing parameter lambda of the EWMA control chart. |
cl |
lower control limit of the EWMA control chart. |
cu |
upper control limit of the EWMA control chart. |
sigma |
true standard deviation. |
df |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
s2.on |
distinguishes between |
hs |
so-called headstart (enables fast initial response);
the default ( |
sided |
distinguishes between one- and two-sided
two-sided EWMA- |
r |
dimension of the resulting linear equation system (highest order of the collocation polynomials). |
qm |
number of quadrature nodes for calculating the collocation definite integrals. |
sewma.arl
determines the Average Run Length (ARL) by numerically
solving the related ARL integral equation by means of
collocation (Chebyshev polynomials).
Returns a single value which resembles the ARL.
Sven Knoth
S. Knoth (2005),
Accurate ARL computation for EWMA- control charts,
Statistics and Computing 15, 341-352.
S. Knoth (2006),
Computation of the ARL for CUSUM- schemes,
Computational Statistics & Data Analysis 51, 499-512.
xewma.arl
for zero-state ARL computation of EWMA control charts
for monitoring normal mean.
## Knoth (2005) ## compare with Table 1 (p. 347): 249.9997 ## Monte Carlo with 10^9 replicates: 249.9892 +/- 0.008 l <- .025 df <- 1 cu <- 1 + 1.661865*sqrt(l/(2-l))*sqrt(2/df) sewma.arl(l,0,cu,1,df) ## ARL values for upper and lower EWMA charts with reflecting barriers ## (reflection at in-control level sigma0 = 1) ## examples from Knoth (2006), Tables 4 and 5 Ssewma.arl <- Vectorize("sewma.arl", "sigma") ## upper chart with reflection at sigma0=1 in Table 4 ## original entries are # sigma ARL # 1 100.0 # 1.01 85.3 # 1.02 73.4 # 1.03 63.5 # 1.04 55.4 # 1.05 48.7 # 1.1 27.9 # 1.2 12.9 # 1.3 7.86 # 1.4 5.57 # 1.5 4.30 # 2 2.11 ## Not run: l <- 0.15 df <- 4 cu <- 1 + 2.4831*sqrt(l/(2-l))*sqrt(2/df) sigmas <- c(1 + (0:5)/100, 1 + (1:5)/10, 2) arls <- round(Ssewma.arl(l, 1, cu, sigmas, df, sided="Rupper", r=100), digits=2) data.frame(sigmas, arls) ## End(Not run) ## lower chart with reflection at sigma0=1 in Table 5 ## original entries are # sigma ARL # 1 200.04 # 0.9 38.47 # 0.8 14.63 # 0.7 8.65 # 0.6 6.31 ## Not run: l <- 0.115 df <- 5 cl <- 1 - 2.0613*sqrt(l/(2-l))*sqrt(2/df) sigmas <- c((10:6)/10) arls <- round(Ssewma.arl(l, cl, 1, sigmas, df, sided="Rlower", r=100), digits=2) data.frame(sigmas, arls) ## End(Not run)
## Knoth (2005) ## compare with Table 1 (p. 347): 249.9997 ## Monte Carlo with 10^9 replicates: 249.9892 +/- 0.008 l <- .025 df <- 1 cu <- 1 + 1.661865*sqrt(l/(2-l))*sqrt(2/df) sewma.arl(l,0,cu,1,df) ## ARL values for upper and lower EWMA charts with reflecting barriers ## (reflection at in-control level sigma0 = 1) ## examples from Knoth (2006), Tables 4 and 5 Ssewma.arl <- Vectorize("sewma.arl", "sigma") ## upper chart with reflection at sigma0=1 in Table 4 ## original entries are # sigma ARL # 1 100.0 # 1.01 85.3 # 1.02 73.4 # 1.03 63.5 # 1.04 55.4 # 1.05 48.7 # 1.1 27.9 # 1.2 12.9 # 1.3 7.86 # 1.4 5.57 # 1.5 4.30 # 2 2.11 ## Not run: l <- 0.15 df <- 4 cu <- 1 + 2.4831*sqrt(l/(2-l))*sqrt(2/df) sigmas <- c(1 + (0:5)/100, 1 + (1:5)/10, 2) arls <- round(Ssewma.arl(l, 1, cu, sigmas, df, sided="Rupper", r=100), digits=2) data.frame(sigmas, arls) ## End(Not run) ## lower chart with reflection at sigma0=1 in Table 5 ## original entries are # sigma ARL # 1 200.04 # 0.9 38.47 # 0.8 14.63 # 0.7 8.65 # 0.6 6.31 ## Not run: l <- 0.115 df <- 5 cl <- 1 - 2.0613*sqrt(l/(2-l))*sqrt(2/df) sigmas <- c((10:6)/10) arls <- round(Ssewma.arl(l, cl, 1, sigmas, df, sided="Rlower", r=100), digits=2) data.frame(sigmas, arls) ## End(Not run)
Computation of the (zero-state) Average Run Length (ARL)
for EWMA control charts (based on the sample variance )
monitoring normal variance with estimated parameters.
sewma.arl.prerun(l, cl, cu, sigma, df1, df2, hs=1, sided="upper", r=40, qm=30, qm.sigma=30, truncate=1e-10)
sewma.arl.prerun(l, cl, cu, sigma, df1, df2, hs=1, sided="upper", r=40, qm=30, qm.sigma=30, truncate=1e-10)
l |
smoothing parameter lambda of the EWMA control chart. |
cl |
lower control limit of the EWMA control chart. |
cu |
upper control limit of the EWMA control chart. |
sigma |
true standard deviation. |
df1 |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
df2 |
degrees of freedom of the pre-run variance estimator. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided two-sided EWMA- |
r |
dimension of the resulting linear equation system (highest order of the collocation polynomials). |
qm |
number of quadrature nodes for calculating the collocation definite integrals. |
qm.sigma |
number of quadrature nodes for convoluting the standard deviation uncertainty. |
truncate |
size of truncated tail. |
Essentially, the ARL function sewma.arl
is convoluted with the
distribution of the sample standard deviation.
For details see Jones/Champ/Rigdon (2001) and Knoth (2014?).
Returns a single value which resembles the ARL.
Sven Knoth
L. A. Jones, C. W. Champ, S. E. Rigdon (2001), The performance of exponentially weighted moving average charts with estimated parameters, Technometrics 43, 156-167.
S. Knoth (2005),
Accurate ARL computation for EWMA- control charts,
Statistics and Computing 15, 341-352.
S. Knoth (2006),
Computation of the ARL for CUSUM- schemes,
Computational Statistics & Data Analysis 51, 499-512.
sewma.arl
for zero-state ARL function of EWMA control charts w/o pre run uncertainty.
## will follow
## will follow
Computation of the critical values (similar to alarm limits)
for different types of EWMA control charts (based on the sample variance
) monitoring normal variance.
sewma.crit(l,L0,df,sigma0=1,cl=NULL,cu=NULL,hs=NULL,s2.on=TRUE, sided="upper",mode="fixed",ur=4,r=40,qm=30)
sewma.crit(l,L0,df,sigma0=1,cl=NULL,cu=NULL,hs=NULL,s2.on=TRUE, sided="upper",mode="fixed",ur=4,r=40,qm=30)
l |
smoothing parameter lambda of the EWMA control chart. |
L0 |
in-control ARL. |
df |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
sigma0 |
in-control standard deviation. |
cl |
deployed for |
cu |
for two-sided ( |
hs |
so-called headstart (enables fast initial response); the default ( |
s2.on |
distinguishes between |
sided |
distinguishes between one- and two-sided
two-sided EWMA- |
mode |
only deployed for |
ur |
truncation of lower chart for |
r |
dimension of the resulting linear equation system (highest order of the collocation polynomials). |
qm |
number of quadrature nodes for calculating the collocation definite integrals. |
sewma.crit
determines the critical values (similar to alarm limits)
for given in-control ARL L0
by applying secant rule and using sewma.arl()
.
In case of sided
="two"
and mode
="unbiased"
a two-dimensional secant rule is applied that also ensures that the
maximum of the ARL function for given standard deviation is attained
at sigma0
. See Knoth (2010) and the related example.
Returns the lower and upper control limit cl
and cu
.
Sven Knoth
H.-J. Mittag and D. Stemann and B. Tewes (1998), EWMA-Karten zur \"Uberwachung der Streuung von Qualit\"atsmerkmalen, Allgemeines Statistisches Archiv 82, 327-338,
C. A. Acosta-Mej\'ia and J. J. Pignatiello Jr. and B. V. Rao (1999), A comparison of control charting procedures for monitoring process dispersion, IIE Transactions 31, 569-579.
S. Knoth (2005),
Accurate ARL computation for EWMA- control charts,
Statistics and Computing 15, 341-352.
S. Knoth (2006a),
Computation of the ARL for CUSUM- schemes,
Computational Statistics & Data Analysis 51, 499-512.
S. Knoth (2006b), The art of evaluating monitoring schemes – how to measure the performance of control charts? in Frontiers in Statistical Quality Control 8, H.-J. Lenz and P.-T. Wilrich (Eds.), Physica Verlag, Heidelberg, Germany, 74-99.
S. Knoth (2010), Control Charting Normal Variance – Reflections, Curiosities, and Recommendations, in Frontiers in Statistical Quality Control 9, H.-J. Lenz and P.-T. Wilrich (Eds.), Physica Verlag, Heidelberg, Germany, 3-18.
sewma.arl
for calculation of ARL of variance charts.
## Mittag et al. (1998) ## compare their upper critical value 2.91 that ## leads to the upper control limit via the formula shown below ## (for the usual upper EWMA \eqn{S^2}{S^2}). ## See Knoth (2006b) for a discussion of this EWMA setup and it's evaluation. l <- 0.18 L0 <- 250 df <- 4 limits <- sewma.crit(l, L0, df) limits["cu"] limits.cu.mittag_et_al <- 1 + sqrt(l/(2-l))*sqrt(2/df)*2.91 limits.cu.mittag_et_al ## Knoth (2005) ## reproduce the critical value given in Figure 2 (c=1.661865) for ## upper EWMA \eqn{S^2}{S^2} with df=1 l <- 0.025 L0 <- 250 df <- 1 limits <- sewma.crit(l, L0, df) cv.Fig2 <- (limits["cu"]-1)/( sqrt(l/(2-l))*sqrt(2/df) ) cv.Fig2 ## the small difference (sixth digit after decimal point) stems from ## tighter criterion in the secant rule implemented in the R package. ## demo of unbiased ARL curves ## Deploy, please, not matrix dimensions smaller than 50 -- for the ## sake of accuracy, the value 80 was used. ## Additionally, this example needs between 1 and 2 minutes on a 1.6 Ghz box. ## Not run: l <- 0.1 L0 <- 500 df <- 4 limits <- sewma.crit(l, L0, df, sided="two", mode="unbiased", r=80) SEWMA.arl <- Vectorize(sewma.arl, "sigma") SEWMA.ARL <- function(sigma) SEWMA.arl(l, limits[1], limits[2], sigma, df, sided="two", r=80) layout(matrix(1:2, nrow=1)) curve(SEWMA.ARL, .75, 1.25, log="y") curve(SEWMA.ARL, .95, 1.05, log="y") ## End(Not run) # the above stuff needs about 1 minute ## control limits for upper and lower EWMA charts with reflecting barriers ## (reflection at in-control level sigma0 = 1) ## examples from Knoth (2006a), Tables 4 and 5 ## Not run: ## upper chart with reflection at sigma0=1 in Table 4: c = 2.4831 l <- 0.15 L0 <- 100 df <- 4 limits <- sewma.crit(l, L0, df, cl=1, sided="Rupper", r=100) cv.Tab4 <- (limits["cu"]-1)/( sqrt(l/(2-l))*sqrt(2/df) ) cv.Tab4 ## lower chart with reflection at sigma0=1 in Table 5: c = 2.0613 l <- 0.115 L0 <- 200 df <- 5 limits <- sewma.crit(l, L0, df, cu=1, sided="Rlower", r=100) cv.Tab5 <- -(limits["cl"]-1)/( sqrt(l/(2-l))*sqrt(2/df) ) cv.Tab5 ## End(Not run)
## Mittag et al. (1998) ## compare their upper critical value 2.91 that ## leads to the upper control limit via the formula shown below ## (for the usual upper EWMA \eqn{S^2}{S^2}). ## See Knoth (2006b) for a discussion of this EWMA setup and it's evaluation. l <- 0.18 L0 <- 250 df <- 4 limits <- sewma.crit(l, L0, df) limits["cu"] limits.cu.mittag_et_al <- 1 + sqrt(l/(2-l))*sqrt(2/df)*2.91 limits.cu.mittag_et_al ## Knoth (2005) ## reproduce the critical value given in Figure 2 (c=1.661865) for ## upper EWMA \eqn{S^2}{S^2} with df=1 l <- 0.025 L0 <- 250 df <- 1 limits <- sewma.crit(l, L0, df) cv.Fig2 <- (limits["cu"]-1)/( sqrt(l/(2-l))*sqrt(2/df) ) cv.Fig2 ## the small difference (sixth digit after decimal point) stems from ## tighter criterion in the secant rule implemented in the R package. ## demo of unbiased ARL curves ## Deploy, please, not matrix dimensions smaller than 50 -- for the ## sake of accuracy, the value 80 was used. ## Additionally, this example needs between 1 and 2 minutes on a 1.6 Ghz box. ## Not run: l <- 0.1 L0 <- 500 df <- 4 limits <- sewma.crit(l, L0, df, sided="two", mode="unbiased", r=80) SEWMA.arl <- Vectorize(sewma.arl, "sigma") SEWMA.ARL <- function(sigma) SEWMA.arl(l, limits[1], limits[2], sigma, df, sided="two", r=80) layout(matrix(1:2, nrow=1)) curve(SEWMA.ARL, .75, 1.25, log="y") curve(SEWMA.ARL, .95, 1.05, log="y") ## End(Not run) # the above stuff needs about 1 minute ## control limits for upper and lower EWMA charts with reflecting barriers ## (reflection at in-control level sigma0 = 1) ## examples from Knoth (2006a), Tables 4 and 5 ## Not run: ## upper chart with reflection at sigma0=1 in Table 4: c = 2.4831 l <- 0.15 L0 <- 100 df <- 4 limits <- sewma.crit(l, L0, df, cl=1, sided="Rupper", r=100) cv.Tab4 <- (limits["cu"]-1)/( sqrt(l/(2-l))*sqrt(2/df) ) cv.Tab4 ## lower chart with reflection at sigma0=1 in Table 5: c = 2.0613 l <- 0.115 L0 <- 200 df <- 5 limits <- sewma.crit(l, L0, df, cu=1, sided="Rlower", r=100) cv.Tab5 <- -(limits["cl"]-1)/( sqrt(l/(2-l))*sqrt(2/df) ) cv.Tab5 ## End(Not run)
Computation of quantiles of the Run Length (RL) for EWMA control charts monitoring normal variance.
sewma.crit.prerun(l,L0,df1,df2,sigma0=1,cl=NULL,cu=NULL,hs=1,sided="upper", mode="fixed",r=40,qm=30,qm.sigma=30,truncate=1e-10, tail_approx=TRUE,c.error=1e-10,a.error=1e-9)
sewma.crit.prerun(l,L0,df1,df2,sigma0=1,cl=NULL,cu=NULL,hs=1,sided="upper", mode="fixed",r=40,qm=30,qm.sigma=30,truncate=1e-10, tail_approx=TRUE,c.error=1e-10,a.error=1e-9)
l |
smoothing parameter lambda of the EWMA control chart. |
L0 |
in-control quantile value. |
df1 |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
df2 |
degrees of freedom of the pre-run variance estimator. |
sigma , sigma0
|
true and in-control standard deviation, respectively. |
cl |
deployed for |
cu |
for two-sided ( |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided two-sided EWMA- |
mode |
only deployed for |
r |
dimension of the resulting linear equation system (highest order of the collocation polynomials). |
qm |
number of quadrature nodes for calculating the collocation definite integrals. |
qm.sigma |
number of quadrature nodes for convoluting the standard deviation uncertainty. |
truncate |
size of truncated tail. |
tail_approx |
controls whether the geometric tail approximation is used (is faster) or not. |
c.error |
error bound for two succeeding values of the critical value during applying the secant rule. |
a.error |
error bound for the quantile level |
sewma.crit.prerun
determines the critical values (similar to alarm limits)
for given in-control ARL L0
by applying secant rule and using sewma.arl.prerun()
.
In case of sided
="two"
and mode
="unbiased"
a two-dimensional secant rule is applied that also ensures that the
maximum of the ARL function for given standard deviation is attained
at sigma0
. See Knoth (2010) for some details of the algorithm involved.
Returns the lower and upper control limit cl
and cu
.
Sven Knoth
H.-J. Mittag and D. Stemann and B. Tewes (1998),
EWMA-Karten zur \"Uberwachung der Streuung von Qualit\"atsmerkmalen,
Allgemeines Statistisches Archiv 82, 327-338,
S. Knoth (2005),
Accurate ARL computation for EWMA- control charts,
Statistics and Computing 15, 341-352.
S. Knoth (2010), Control Charting Normal Variance – Reflections, Curiosities, and Recommendations, in Frontiers in Statistical Quality Control 9, H.-J. Lenz and P.-T. Wilrich (Eds.), Physica Verlag, Heidelberg, Germany, 3-18.
sewma.arl.prerun
for calculation of ARL of variance charts under
pre-run uncertainty and sewma.crit
for
the algorithm w/o pre-run uncertainty.
## will follow
## will follow
Computation of quantiles of the Run Length (RL) for EWMA control charts monitoring normal variance.
sewma.q(l, cl, cu, sigma, df, alpha, hs=1, sided="upper", r=40, qm=30) sewma.q.crit(l,L0,alpha,df,sigma0=1,cl=NULL,cu=NULL,hs=1,sided="upper", mode="fixed",ur=4,r=40,qm=30,c.error=1e-12,a.error=1e-9)
sewma.q(l, cl, cu, sigma, df, alpha, hs=1, sided="upper", r=40, qm=30) sewma.q.crit(l,L0,alpha,df,sigma0=1,cl=NULL,cu=NULL,hs=1,sided="upper", mode="fixed",ur=4,r=40,qm=30,c.error=1e-12,a.error=1e-9)
l |
smoothing parameter lambda of the EWMA control chart. |
cl |
deployed for |
cu |
for two-sided ( |
sigma , sigma0
|
true and in-control standard deviation, respectively. |
df |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
alpha |
quantile level. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided two-sided EWMA- |
mode |
only deployed for |
ur |
truncation of lower chart for |
r |
dimension of the resulting linear equation system (highest order of the collocation polynomials). |
qm |
number of quadrature nodes for calculating the collocation definite integrals. |
L0 |
in-control quantile value. |
c.error |
error bound for two succeeding values of the critical value during applying the secant rule. |
a.error |
error bound for the quantile level |
Instead of the popular ARL (Average Run Length) quantiles of the EWMA
stopping time (Run Length) are determined. The algorithm is based on
Waldmann's survival function iteration procedure.
Thereby the ideas presented in Knoth (2007) are used.
sewma.q.crit
determines the critical values (similar to alarm limits)
for given in-control RL quantile L0
at level alpha
by applying
secant rule and using sewma.sf()
.
In case of sided
="two"
and mode
="unbiased"
a two-dimensional
secant rule is applied that also ensures that the
minimum of the cdf for given standard deviation is attained at sigma0
.
Returns a single value which resembles the RL quantile of order alpha
and
the lower and upper control limit cl
and cu
, respectively.
Sven Knoth
H.-J. Mittag and D. Stemann and B. Tewes (1998), EWMA-Karten zur \"Uberwachung der Streuung von Qualit\"atsmerkmalen, Allgemeines Statistisches Archiv 82, 327-338,
C. A. Acosta-Mej\'ia and J. J. Pignatiello Jr. and B. V. Rao (1999), A comparison of control charting procedures for monitoring process dispersion, IIE Transactions 31, 569-579.
S. Knoth (2005),
Accurate ARL computation for EWMA- control charts,
Statistics and Computing 15, 341-352.
S. Knoth (2007), Accurate ARL calculation for EWMA control charts monitoring simultaneously normal mean and variance, Sequential Analysis 26, 251-264.
S. Knoth (2010), Control Charting Normal Variance – Reflections, Curiosities, and Recommendations, in Frontiers in Statistical Quality Control 9, H.-J. Lenz and P.-T. Wilrich (Eds.), Physica Verlag, Heidelberg, Germany, 3-18.
K.-H. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, Appl. Statist. 35, 151-158.
sewma.arl
for calculation of ARL of variance charts and
sewma.sf
for the RL survival function.
## will follow
## will follow
Computation of quantiles of the Run Length (RL) for EWMA control charts monitoring normal variance.
sewma.q.prerun(l,cl,cu,sigma,df1,df2,alpha,hs=1,sided="upper", r=40,qm=30,qm.sigma=30,truncate=1e-10) sewma.q.crit.prerun(l,L0,alpha,df1,df2,sigma0=1,cl=NULL,cu=NULL,hs=1, sided="upper",mode="fixed",r=40, qm=30,qm.sigma=30,truncate=1e-10, tail_approx=TRUE,c.error=1e-10,a.error=1e-9)
sewma.q.prerun(l,cl,cu,sigma,df1,df2,alpha,hs=1,sided="upper", r=40,qm=30,qm.sigma=30,truncate=1e-10) sewma.q.crit.prerun(l,L0,alpha,df1,df2,sigma0=1,cl=NULL,cu=NULL,hs=1, sided="upper",mode="fixed",r=40, qm=30,qm.sigma=30,truncate=1e-10, tail_approx=TRUE,c.error=1e-10,a.error=1e-9)
l |
smoothing parameter lambda of the EWMA control chart. |
cl |
deployed for |
cu |
for two-sided ( |
sigma , sigma0
|
true and in-control standard deviation, respectively. |
L0 |
in-control quantile value. |
alpha |
quantile level. |
df1 |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
df2 |
degrees of freedom of the pre-run variance estimator. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided two-sided EWMA- |
mode |
only deployed for |
r |
dimension of the resulting linear equation system (highest order of the collocation polynomials). |
qm |
number of quadrature nodes for calculating the collocation definite integrals. |
qm.sigma |
number of quadrature nodes for convoluting the standard deviation uncertainty. |
truncate |
size of truncated tail. |
tail_approx |
controls whether the geometric tail approximation is used (is faster) or not. |
c.error |
error bound for two succeeding values of the critical value during applying the secant rule. |
a.error |
error bound for the quantile level |
Instead of the popular ARL (Average Run Length) quantiles of the EWMA
stopping time (Run Length) are determined. The algorithm is based on
Waldmann's survival function iteration procedure.
Thereby the ideas presented in Knoth (2007) are used.
sewma.q.crit.prerun
determines the critical values (similar to alarm limits)
for given in-control RL quantile L0
at level alpha
by applying secant
rule and using sewma.sf()
.
In case of sided
="two"
and mode
="unbiased"
a two-dimensional secant rule is applied that also ensures that the
minimum of the cdf for given standard deviation is attained at sigma0
.
Returns a single value which resembles the RL quantile of order alpha
and
the lower and upper control limit cl
and cu
, respectively.
Sven Knoth
S. Knoth (2007), Accurate ARL calculation for EWMA control charts monitoring simultaneously normal mean and variance, Sequential Analysis 26, 251-264.
K.-H. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, Appl. Statist. 35, 151-158.
sewma.q
and sewma.q.crit
for the version w/o pre-run uncertainty.
## will follow
## will follow
Computation of the survival function of the Run Length (RL) for EWMA control charts monitoring normal variance.
sewma.sf(n, l, cl, cu, sigma, df, hs=1, sided="upper", r=40, qm=30)
sewma.sf(n, l, cl, cu, sigma, df, hs=1, sided="upper", r=40, qm=30)
n |
calculate sf up to value |
l |
smoothing parameter lambda of the EWMA control chart. |
cl |
lower control limit of the EWMA control chart. |
cu |
upper control limit of the EWMA control chart. |
sigma |
true standard deviation. |
df |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided two-sided
EWMA- |
r |
dimension of the resulting linear equation system (highest order of the collocation polynomials). |
qm |
number of quadrature nodes for calculating the collocation definite integrals. |
The survival function P(L>n) and derived from it also the cdf P(L<=n) and the pmf P(L=n) illustrate the distribution of the EWMA run length. For large n the geometric tail could be exploited. That is, with reasonable large n the complete distribution is characterized. The algorithm is based on Waldmann's survival function iteration procedure and on results in Knoth (2007).
Returns a vector which resembles the survival function up to a certain point.
Sven Knoth
S. Knoth (2007), Accurate ARL calculation for EWMA control charts monitoring simultaneously normal mean and variance, Sequential Analysis 26, 251-264.
K.-H. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, Appl. Statist. 35, 151-158.
sewma.arl
for zero-state ARL computation of variance EWMA control charts.
## will follow
## will follow
Computation of the survival function of the Run Length (RL) for EWMA control charts monitoring normal variance.
sewma.sf.prerun(n, l, cl, cu, sigma, df1, df2, hs=1, sided="upper", qm=30, qm.sigma=30, truncate=1e-10, tail_approx=TRUE)
sewma.sf.prerun(n, l, cl, cu, sigma, df1, df2, hs=1, sided="upper", qm=30, qm.sigma=30, truncate=1e-10, tail_approx=TRUE)
n |
calculate sf up to value |
l |
smoothing parameter lambda of the EWMA control chart. |
cl |
lower control limit of the EWMA control chart. |
cu |
upper control limit of the EWMA control chart. |
sigma |
true standard deviation. |
df1 |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
df2 |
degrees of freedom of the pre-run variance estimator. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided two-sided
EWMA- |
qm |
number of quadrature nodes for calculating the collocation definite integrals. |
qm.sigma |
number of quadrature nodes for convoluting the standard deviation uncertainty. |
truncate |
size of truncated tail. |
tail_approx |
Controls whether the geometric tail approximation is used (is faster) or not. |
The survival function P(L>n) and derived from it also the cdf P(L<=n) and the pmf P(L=n) illustrate the distribution of the EWMA run length. For large n the geometric tail could be exploited. That is, with reasonable large n the complete distribution is characterized. The algorithm is based on Waldmann's survival function iteration procedure and on results in Knoth (2007)...
Returns a vector which resembles the survival function up to a certain point.
Sven Knoth
S. Knoth (2007), Accurate ARL calculation for EWMA control charts monitoring simultaneously normal mean and variance, Sequential Analysis 26, 251-264.
K.-H. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, Appl. Statist. 35, 151-158.
sewma.sf
for the RL survival function of EWMA control charts w/o pre-run uncertainty.
## will follow
## will follow
Computation of the (zero-state) Average Run Length (ARL) at given Poisson mean mu
.
tewma.arl(lambda, k, lk, uk, mu, z0, rando=FALSE, gl=0, gu=0)
tewma.arl(lambda, k, lk, uk, mu, z0, rando=FALSE, gl=0, gu=0)
lambda |
smoothing parameter of the EWMA p control chart. |
k |
resolution of grid (natural number). |
lk |
lower control limit of the TEWMA control chart, integer. |
uk |
upper control limit of the TEWMA control chart, integer. |
mu |
mean value of Poisson distribution. |
z0 |
so-called headstart (give fast initial response) – it is proposed to use the in-control mean. |
rando |
Distinguish between control chart design without or with randomisation. In the latter case some
meaningful values for |
gl |
randomisation probability at the lower limit. |
gu |
randomisation probability at the upper limit. |
A new idea of applying EWMA smoothing to count data. Here, the thinning operation is
applied to independent Poisson variates is performed.
Moreover, the original thinning principle is expanded to multiples of one over k
to allow finer
grids and finally better detection perfomance. It is highly recommended to read the
corresponding paper (see below).
Return single value which resemble the ARL.
Sven Knoth
M. C. Morais, C. H. Weiss, S. Knoth (2019), A thinning-based EWMA chart to monitor counts, submitted.
later.
# MWK (2018) lambda <- 0.1 # (T)EWMA smoothing constant mu0 <- 5 # in-control mean k <- 10 # resolution z0 <- round(k*mu0) # starting value of (T)EWMA sequence # (i) without randomisation lk <- 28 uk <- 75 L0 <- tewma.arl(lambda, k, lk, uk, mu0, z0) # should be 501.9703 # (ii) with randomisation uk <- 76 # lk is not changed gl <- 0.5446310 gu <- 0.1375617 L0 <- tewma.arl(lambda, k, lk, uk, mu0, z0, rando=TRUE, gl=gl, gu=gu) # should be 500
# MWK (2018) lambda <- 0.1 # (T)EWMA smoothing constant mu0 <- 5 # in-control mean k <- 10 # resolution z0 <- round(k*mu0) # starting value of (T)EWMA sequence # (i) without randomisation lk <- 28 uk <- 75 L0 <- tewma.arl(lambda, k, lk, uk, mu0, z0) # should be 501.9703 # (ii) with randomisation uk <- 76 # lk is not changed gl <- 0.5446310 gu <- 0.1375617 L0 <- tewma.arl(lambda, k, lk, uk, mu0, z0, rando=TRUE, gl=gl, gu=gu) # should be 500
For constructing tolerance intervals, which
cover a given proportion of a normal distribution with
unknown mean and variance with confidence
, one needs to calculate
the so-called tolerance limit factors
. These values
are computed for a given sample size
.
tol.lim.fac(n,p,a,mode="WW",m=30)
tol.lim.fac(n,p,a,mode="WW",m=30)
n |
sample size. |
p |
coverage. |
a |
error probability |
mode |
distinguish between Wald/Wolfowitz' approximation method ( |
m |
number of abscissas for the quadrature (needed only for |
tol.lim.fac
determines tolerance limits factors
by means of the fast and simple approximation due to
Wald/Wolfowitz (1946) and of Gauss-Legendre quadrature like Odeh/Owen
(1980), respectively, who used in fact the Simpson Rule. Then, by
one can build the tolerance intervals
which cover at least proportion
of a normal distribution for
given confidence level of
.
and
stand
for the sample mean and the sample standard deviation, respectively.
Returns a single value which resembles the tolerance limit factor.
Sven Knoth
A. Wald, J. Wolfowitz (1946), Tolerance limits for a normal distribution, Annals of Mathematical Statistics 17, 208-215.
R. E. Odeh, D. B. Owen (1980), Tables for Normal Tolerance Limits, Sampling Plans, and Screening, Marcel Dekker, New York.
qnorm
for the ”asymptotic” case – cf. second example.
n <- 2:10 p <- .95 a <- .05 kWW <- sapply(n,p=p,a=a,tol.lim.fac) kEX <- sapply(n,p=p,a=a,mode="exact",tol.lim.fac) print(cbind(n,kWW,kEX),digits=4) ## Odeh/Owen (1980), page 98, in Table 3.4.1 ## n factor k ## 2 36.519 ## 3 9.789 ## 4 6.341 ## 5 5.077 ## 6 4.422 ## 7 4.020 ## 8 3.746 ## 9 3.546 ## 10 3.393 ## n -> infty n <- 10^{1:7} p <- .95 a <- .05 kEX <- round(sapply(n,p=p,a=a,mode="exact",tol.lim.fac),digits=4) kEXinf <- round(qnorm(1-a/2),digits=4) print(rbind(cbind(n,kEX),c("infinity",kEXinf)),quote=FALSE)
n <- 2:10 p <- .95 a <- .05 kWW <- sapply(n,p=p,a=a,tol.lim.fac) kEX <- sapply(n,p=p,a=a,mode="exact",tol.lim.fac) print(cbind(n,kWW,kEX),digits=4) ## Odeh/Owen (1980), page 98, in Table 3.4.1 ## n factor k ## 2 36.519 ## 3 9.789 ## 4 6.341 ## 5 5.077 ## 6 4.422 ## 7 4.020 ## 8 3.746 ## 9 3.546 ## 10 3.393 ## n -> infty n <- 10^{1:7} p <- .95 a <- .05 kEX <- round(sapply(n,p=p,a=a,mode="exact",tol.lim.fac),digits=4) kEXinf <- round(qnorm(1-a/2),digits=4) print(rbind(cbind(n,kEX),c("infinity",kEXinf)),quote=FALSE)
Computation of the (zero-state) Average Run Length (ARL) for EWMA residual control charts monitoring normal mean, variance, or mean and variance simultaneously. Additionally, the probability of misleading signals (PMS) is calculated.
x.res.ewma.arl(l, c, mu, alpha=0, n=5, hs=0, r=40) s.res.ewma.arl(l, cu, sigma, mu=0, alpha=0, n=5, hs=1, r=40, qm=30) xs.res.ewma.arl(lx, cx, ls, csu, mu, sigma, alpha=0, n=5, hsx=0, rx=40, hss=1, rs=40, qm=30) xs.res.ewma.pms(lx, cx, ls, csu, mu, sigma, type="3", alpha=0, n=5, hsx=0, rx=40, hss=1, rs=40, qm=30)
x.res.ewma.arl(l, c, mu, alpha=0, n=5, hs=0, r=40) s.res.ewma.arl(l, cu, sigma, mu=0, alpha=0, n=5, hs=1, r=40, qm=30) xs.res.ewma.arl(lx, cx, ls, csu, mu, sigma, alpha=0, n=5, hsx=0, rx=40, hss=1, rs=40, qm=30) xs.res.ewma.pms(lx, cx, ls, csu, mu, sigma, type="3", alpha=0, n=5, hsx=0, rx=40, hss=1, rs=40, qm=30)
l , lx , ls
|
smoothing parameter(s) lambda of the EWMA control chart. |
c , cu , cx , csu
|
critical value (similar to alarm limit) of the EWMA control charts. |
mu |
true mean. |
sigma |
true standard deviation. |
alpha |
the AR(1) coefficient – first order autocorrelation of the original data. |
n |
batch size. |
hs , hsx , hss
|
so-called headstart (enables fast initial response). |
r , rx , rs
|
number of quadrature nodes or size of collocation base,
dimension of the resulting linear
equation system is equal to |
qm |
number of nodes for collocation quadratures. |
type |
PMS type, for |
The above list of functions provides the application of
algorithms developed for iid data to
the residual case. To be more precise, the underlying model is a sequence of normally
distributed batches with size n
with autocorrelation within
the batch and independence between the batches
(see also the references below). It is restricted to the
classical EWMA chart types, that
is two-sided for the mean, upper charts for the variance,
and all equipped with fixed limits.
The autocorrelation is modeled by an AR(1) process with parameter
alpha
. Additionally,
with xs.res.ewma.pms
the probability of misleading signals
(PMS) of type
is
calculated. This is offered exclusively in this small
collection so that for iid data
this function has to be used too (with alpha=0
).
Return single values which resemble the ARL and the PMS, respectively.
Sven Knoth
S. Knoth, M. C. Morais, A. Pacheco, W. Schmid (2009), Misleading Signals in Simultaneous Residual Schemes for the Mean and Variance of a Stationary Process, Commun. Stat., Theory Methods 38, 2923-2943.
S. Knoth, W. Schmid, A. Schoene (2001), Simultaneous Shewhart-Type Charts for the Mean and the Variance of a Time Series, Frontiers of Statistical Quality Control 6, A. Lenz, H.-J. & Wilrich, P.-T. (Eds.), 6, 61-79.
S. Knoth, W. Schmid (2002) Monitoring the mean and the variance of a stationary process, Statistica Neerlandica 56, 77-100.
xewma.arl
, sewma.arl
, and xsewma.arl
as more
elaborated functions in the iid case.
## Not run: ## S. Knoth, W. Schmid (2002) cat("\nFragments of Table 2 (n=5, lambda.1=lambda.2)\n") lambdas <- c(.5, .25, .1, .05) L0 <- 500 n <- 5 crit <- NULL for ( lambda in lambdas ) { cs <- xsewma.crit(lambda, lambda, L0, n-1) x.e <- round(cs[1], digits=4) names(x.e) <- NULL s.e <- round((cs[3]-1) * sqrt((2-lambda)/lambda)*sqrt((n-1)/2), digits=4) names(s.e) <- NULL crit <- rbind(crit, data.frame(lambda, x.e, s.e)) } ## orinal values are (Markov chain approximation with 50 states) # lambda x.e s.e # 0.50 3.2765 4.6439 # 0.25 3.2168 4.0149 # 0.10 3.0578 3.3376 # 0.05 2.8817 2.9103 print(crit) cat("\nFragments of Table 4 (n=5, lambda.1=lambda.2=0.1)\n\n") lambda <- .1 # the algorithm used in Knoth/Schmid is less accurate -- proceed with their values cx <- x.e <- 3.0578 s.e <- 3.3376 csu <- 1 + s.e * sqrt(lambda/(2-lambda))*sqrt(2/(n-1)) alpha <- .3 a.values <- c((0:6)/4, 2) d.values <- c(1 + (0:5)/10, 1.75 , 2) arls <- NULL for ( delta in d.values ) { row <- NULL for ( mu in a.values ) { arl <- round(xs.res.ewma.arl(lambda, cx, lambda, csu, mu*sqrt(n), delta, alpha=alpha, n=n), digits=2) names(arl) <- NULL row <- c(row, arl) } arls <- rbind(arls, data.frame(t(row))) } names(arls) <- a.values rownames(arls) <- d.values ## orinal values are (now Monte-Carlo with 10^6 replicates) # 0 0.25 0.5 0.75 1 1.25 1.5 2 #1 502.44 49.50 14.21 7.93 5.53 4.28 3.53 2.65 #1.1 73.19 32.91 13.33 7.82 5.52 4.29 3.54 2.66 #1.2 24.42 18.88 11.37 7.44 5.42 4.27 3.54 2.67 #1.3 13.11 11.83 9.09 6.74 5.18 4.17 3.50 2.66 #1.4 8.74 8.31 7.19 5.89 4.81 4.00 3.41 2.64 #1.5 6.50 6.31 5.80 5.08 4.37 3.76 3.28 2.59 #1.75 3.94 3.90 3.78 3.59 3.35 3.09 2.83 2.40 #2 2.85 2.84 2.80 2.73 2.63 2.51 2.39 2.14 print(arls) ## S. Knoth, M. C. Morais, A. Pacheco, W. Schmid (2009) cat("\nFragments of Table 5 (n=5, lambda=0.1)\n\n") d.values <- c(1.02, 1 + (1:5)/10, 1.75 , 2) arl.x <- arl.s <- arl.xs <- PMS.3 <- NULL for ( delta in d.values ) { arl.x <- c(arl.x, round(x.res.ewma.arl(lambda, cx/delta, 0, n=n), digits=3)) arl.s <- c(arl.s, round(s.res.ewma.arl(lambda, csu, delta, n=n), digits=3)) arl.xs <- c(arl.xs, round(xs.res.ewma.arl(lambda, cx, lambda, csu, 0, delta, n=n), digits=3)) PMS.3 <- c(PMS.3, round(xs.res.ewma.pms(lambda, cx, lambda, csu, 0, delta, n=n), digits=6)) } ## orinal values are (Markov chain approximation) # delta arl.x arl.s arl.xs PMS.3 # 1.02 833.086 518.935 323.324 0.381118 # 1.10 454.101 84.208 73.029 0.145005 # 1.20 250.665 25.871 24.432 0.071024 # 1.30 157.343 13.567 13.125 0.047193 # 1.40 108.112 8.941 8.734 0.035945 # 1.50 79.308 6.614 6.493 0.029499 # 1.75 44.128 3.995 3.942 0.021579 # 2.00 28.974 2.887 2.853 0.018220 print(cbind(delta=d.values, arl.x, arl.s, arl.xs, PMS.3)) cat("\nFragments of Table 6 (n=5, lambda=0.1)\n\n") alphas <- c(-0.9, -0.5, -0.3, 0, 0.3, 0.5, 0.9) deltas <- c(0.05, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 2) PMS.4 <- NULL for ( ir in 1:length(deltas) ) { mu <- deltas[ir]*sqrt(n) pms <- NULL for ( alpha in alphas ) { pms <- c(pms, round(xs.res.ewma.pms(lambda, cx, lambda, csu, mu, 1, type="4", alpha=alpha, n=n), digits=6)) } PMS.4 <- rbind(PMS.4, data.frame(delta=deltas[ir], t(pms))) } names(PMS.4) <- c("delta", alphas) rownames(PMS.4) <- NULL ## orinal values are (Markov chain approximation) # delta -0.9 -0.5 -0.3 0 0.3 0.5 0.9 # 0.05 0.055789 0.224521 0.279842 0.342805 0.391299 0.418915 0.471386 # 0.25 0.003566 0.009522 0.014580 0.025786 0.044892 0.066584 0.192023 # 0.50 0.002994 0.001816 0.002596 0.004774 0.009259 0.015303 0.072945 # 0.75 0.006967 0.000703 0.000837 0.001529 0.003400 0.006424 0.046602 # 1.00 0.005098 0.000402 0.000370 0.000625 0.001589 0.003490 0.039978 # 1.25 0.000084 0.000266 0.000202 0.000300 0.000867 0.002220 0.039773 # 1.50 0.000000 0.000256 0.000120 0.000163 0.000531 0.001584 0.042734 # 2.00 0.000000 0.000311 0.000091 0.000056 0.000259 0.001029 0.054543 print(PMS.4) ## End(Not run)
## Not run: ## S. Knoth, W. Schmid (2002) cat("\nFragments of Table 2 (n=5, lambda.1=lambda.2)\n") lambdas <- c(.5, .25, .1, .05) L0 <- 500 n <- 5 crit <- NULL for ( lambda in lambdas ) { cs <- xsewma.crit(lambda, lambda, L0, n-1) x.e <- round(cs[1], digits=4) names(x.e) <- NULL s.e <- round((cs[3]-1) * sqrt((2-lambda)/lambda)*sqrt((n-1)/2), digits=4) names(s.e) <- NULL crit <- rbind(crit, data.frame(lambda, x.e, s.e)) } ## orinal values are (Markov chain approximation with 50 states) # lambda x.e s.e # 0.50 3.2765 4.6439 # 0.25 3.2168 4.0149 # 0.10 3.0578 3.3376 # 0.05 2.8817 2.9103 print(crit) cat("\nFragments of Table 4 (n=5, lambda.1=lambda.2=0.1)\n\n") lambda <- .1 # the algorithm used in Knoth/Schmid is less accurate -- proceed with their values cx <- x.e <- 3.0578 s.e <- 3.3376 csu <- 1 + s.e * sqrt(lambda/(2-lambda))*sqrt(2/(n-1)) alpha <- .3 a.values <- c((0:6)/4, 2) d.values <- c(1 + (0:5)/10, 1.75 , 2) arls <- NULL for ( delta in d.values ) { row <- NULL for ( mu in a.values ) { arl <- round(xs.res.ewma.arl(lambda, cx, lambda, csu, mu*sqrt(n), delta, alpha=alpha, n=n), digits=2) names(arl) <- NULL row <- c(row, arl) } arls <- rbind(arls, data.frame(t(row))) } names(arls) <- a.values rownames(arls) <- d.values ## orinal values are (now Monte-Carlo with 10^6 replicates) # 0 0.25 0.5 0.75 1 1.25 1.5 2 #1 502.44 49.50 14.21 7.93 5.53 4.28 3.53 2.65 #1.1 73.19 32.91 13.33 7.82 5.52 4.29 3.54 2.66 #1.2 24.42 18.88 11.37 7.44 5.42 4.27 3.54 2.67 #1.3 13.11 11.83 9.09 6.74 5.18 4.17 3.50 2.66 #1.4 8.74 8.31 7.19 5.89 4.81 4.00 3.41 2.64 #1.5 6.50 6.31 5.80 5.08 4.37 3.76 3.28 2.59 #1.75 3.94 3.90 3.78 3.59 3.35 3.09 2.83 2.40 #2 2.85 2.84 2.80 2.73 2.63 2.51 2.39 2.14 print(arls) ## S. Knoth, M. C. Morais, A. Pacheco, W. Schmid (2009) cat("\nFragments of Table 5 (n=5, lambda=0.1)\n\n") d.values <- c(1.02, 1 + (1:5)/10, 1.75 , 2) arl.x <- arl.s <- arl.xs <- PMS.3 <- NULL for ( delta in d.values ) { arl.x <- c(arl.x, round(x.res.ewma.arl(lambda, cx/delta, 0, n=n), digits=3)) arl.s <- c(arl.s, round(s.res.ewma.arl(lambda, csu, delta, n=n), digits=3)) arl.xs <- c(arl.xs, round(xs.res.ewma.arl(lambda, cx, lambda, csu, 0, delta, n=n), digits=3)) PMS.3 <- c(PMS.3, round(xs.res.ewma.pms(lambda, cx, lambda, csu, 0, delta, n=n), digits=6)) } ## orinal values are (Markov chain approximation) # delta arl.x arl.s arl.xs PMS.3 # 1.02 833.086 518.935 323.324 0.381118 # 1.10 454.101 84.208 73.029 0.145005 # 1.20 250.665 25.871 24.432 0.071024 # 1.30 157.343 13.567 13.125 0.047193 # 1.40 108.112 8.941 8.734 0.035945 # 1.50 79.308 6.614 6.493 0.029499 # 1.75 44.128 3.995 3.942 0.021579 # 2.00 28.974 2.887 2.853 0.018220 print(cbind(delta=d.values, arl.x, arl.s, arl.xs, PMS.3)) cat("\nFragments of Table 6 (n=5, lambda=0.1)\n\n") alphas <- c(-0.9, -0.5, -0.3, 0, 0.3, 0.5, 0.9) deltas <- c(0.05, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 2) PMS.4 <- NULL for ( ir in 1:length(deltas) ) { mu <- deltas[ir]*sqrt(n) pms <- NULL for ( alpha in alphas ) { pms <- c(pms, round(xs.res.ewma.pms(lambda, cx, lambda, csu, mu, 1, type="4", alpha=alpha, n=n), digits=6)) } PMS.4 <- rbind(PMS.4, data.frame(delta=deltas[ir], t(pms))) } names(PMS.4) <- c("delta", alphas) rownames(PMS.4) <- NULL ## orinal values are (Markov chain approximation) # delta -0.9 -0.5 -0.3 0 0.3 0.5 0.9 # 0.05 0.055789 0.224521 0.279842 0.342805 0.391299 0.418915 0.471386 # 0.25 0.003566 0.009522 0.014580 0.025786 0.044892 0.066584 0.192023 # 0.50 0.002994 0.001816 0.002596 0.004774 0.009259 0.015303 0.072945 # 0.75 0.006967 0.000703 0.000837 0.001529 0.003400 0.006424 0.046602 # 1.00 0.005098 0.000402 0.000370 0.000625 0.001589 0.003490 0.039978 # 1.25 0.000084 0.000266 0.000202 0.000300 0.000867 0.002220 0.039773 # 1.50 0.000000 0.000256 0.000120 0.000163 0.000531 0.001584 0.042734 # 2.00 0.000000 0.000311 0.000091 0.000056 0.000259 0.001029 0.054543 print(PMS.4) ## End(Not run)
Computation of the steady-state Average Run Length (ARL) for different types of CUSUM control charts monitoring normal mean.
xcusum.ad(k, h, mu1, mu0 = 0, sided = "one", r = 30)
xcusum.ad(k, h, mu1, mu0 = 0, sided = "one", r = 30)
k |
reference value of the CUSUM control chart. |
h |
decision interval (alarm limit, threshold) of the CUSUM control chart. |
mu1 |
out-of-control mean. |
mu0 |
in-control mean. |
sided |
distinguish between one-, two-sided and Crosier's modified
two-sided CUSUM scheme by choosing |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
xcusum.ad
determines the steady-state Average Run Length (ARL)
by numerically solving the related ARL integral equation by means
of the Nystroem method based on Gauss-Legendre quadrature
and using the power method for deriving the largest in magnitude
eigenvalue and the related left eigenfunction.
Returns a single value which resembles the steady-state ARL.
Be cautious in increasing the dimension parameter r
for
two-sided CUSUM schemes. The resulting matrix dimension is r^2
times
r^2
. Thus, go beyond 30 only on fast machines. This is the only case,
were the package routines are based on the Markov chain approach. Moreover,
the two-sided CUSUM scheme needs a two-dimensional Markov chain.
Sven Knoth
R. B. Crosier (1986), A new two-sided cumulative quality control scheme, Technometrics 28, 187-194.
xcusum.arl
for zero-state ARL computation and
xewma.ad
for the steady-state ARL of EWMA control charts.
## comparison of zero-state (= worst case ) and steady-state performance ## for one-sided CUSUM control charts k <- .5 h <- xcusum.crit(k,500) mu <- c(0,.5,1,1.5,2) arl <- sapply(mu,k=k,h=h,xcusum.arl) ad <- sapply(mu,k=k,h=h,xcusum.ad) round(cbind(mu,arl,ad),digits=2) ## Crosier (1986), Crosier's modified two-sided CUSUM ## He introduced the modification and evaluated it by means of ## Markov chain approximation k <- .5 h2 <- 4 hC <- 3.73 mu <- c(0,.25,.5,.75,1,1.5,2,2.5,3,4,5) ad2 <- sapply(mu,k=k,h=h2,sided="two",r=20,xcusum.ad) adC <- sapply(mu,k=k,h=hC,sided="Crosier",xcusum.ad) round(cbind(mu,ad2,adC),digits=2) ## results in the original paper are (in Table 5) ## 0.00 163. 164. ## 0.25 71.6 69.0 ## 0.50 25.2 24.3 ## 0.75 12.3 12.1 ## 1.00 7.68 7.69 ## 1.50 4.31 4.39 ## 2.00 3.03 3.12 ## 2.50 2.38 2.46 ## 3.00 2.00 2.07 ## 4.00 1.55 1.60 ## 5.00 1.22 1.29
## comparison of zero-state (= worst case ) and steady-state performance ## for one-sided CUSUM control charts k <- .5 h <- xcusum.crit(k,500) mu <- c(0,.5,1,1.5,2) arl <- sapply(mu,k=k,h=h,xcusum.arl) ad <- sapply(mu,k=k,h=h,xcusum.ad) round(cbind(mu,arl,ad),digits=2) ## Crosier (1986), Crosier's modified two-sided CUSUM ## He introduced the modification and evaluated it by means of ## Markov chain approximation k <- .5 h2 <- 4 hC <- 3.73 mu <- c(0,.25,.5,.75,1,1.5,2,2.5,3,4,5) ad2 <- sapply(mu,k=k,h=h2,sided="two",r=20,xcusum.ad) adC <- sapply(mu,k=k,h=hC,sided="Crosier",xcusum.ad) round(cbind(mu,ad2,adC),digits=2) ## results in the original paper are (in Table 5) ## 0.00 163. 164. ## 0.25 71.6 69.0 ## 0.50 25.2 24.3 ## 0.75 12.3 12.1 ## 1.00 7.68 7.69 ## 1.50 4.31 4.39 ## 2.00 3.03 3.12 ## 2.50 2.38 2.46 ## 3.00 2.00 2.07 ## 4.00 1.55 1.60 ## 5.00 1.22 1.29
Computation of the (zero-state) Average Run Length (ARL) for different types of CUSUM control charts monitoring normal mean.
xcusum.arl(k, h, mu, hs = 0, sided = "one", method = "igl", q = 1, r = 30)
xcusum.arl(k, h, mu, hs = 0, sided = "one", method = "igl", q = 1, r = 30)
k |
reference value of the CUSUM control chart. |
h |
decision interval (alarm limit, threshold) of the CUSUM control chart. |
mu |
true mean. |
hs |
so-called headstart (give fast initial response). |
sided |
distinguish between one-, two-sided and Crosier's modified
two-sided CUSUM scheme by choosing |
method |
deploy the integral equation ( |
q |
change point position. For |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
xcusum.arl
determines the Average Run Length (ARL) by numerically
solving the related ARL integral equation by means of the Nystroem method
based on Gauss-Legendre quadrature.
Returns a vector of length q
which resembles the ARL and the sequence of conditional expected delays for
q
=1 and q
>1, respectively.
Sven Knoth
A. L. Goel, S. M. Wu (1971), Determination of A.R.L. and a contour nomogram for CUSUM charts to control normal mean, Technometrics 13, 221-230.
D. Brook, D. A. Evans (1972), An approach to the probability distribution of cusum run length, Biometrika 59, 539-548.
J. M. Lucas, R. B. Crosier (1982), Fast initial response for cusum quality-control schemes: Give your cusum a headstart, Technometrics 24, 199-205.
L. C. Vance (1986), Average run lengths of cumulative sum control charts for controlling normal means, Journal of Quality Technology 18, 189-193.
K.-H. Waldmann (1986), Bounds for the distribution of the run length of one-sided and two-sided CUSUM quality control schemes, Technometrics 28, 61-67.
R. B. Crosier (1986), A new two-sided cumulative quality control scheme, Technometrics 28, 187-194.
xewma.arl
for zero-state ARL computation of EWMA control charts
and xcusum.ad
for the steady-state ARL.
## Brook/Evans (1972), one-sided CUSUM ## Their results are based on the less accurate Markov chain approach. k <- .5 h <- 3 round(c( xcusum.arl(k,h,0), xcusum.arl(k,h,1.5) ),digits=2) ## results in the original paper are L0 = 117.59, L1 = 3.75 (in Subsection 4.3). ## Lucas, Crosier (1982) ## (one- and) two-sided CUSUM with possible headstarts k <- .5 h <- 4 mu <- c(0,.25,.5,.75,1,1.5,2,2.5,3,4,5) arl1 <- sapply(mu,k=k,h=h,sided="two",xcusum.arl) arl2 <- sapply(mu,k=k,h=h,hs=h/2,sided="two",xcusum.arl) round(cbind(mu,arl1,arl2),digits=2) ## results in the original paper are (in Table 1) ## 0.00 168. 149. ## 0.25 74.2 62.7 ## 0.50 26.6 20.1 ## 0.75 13.3 8.97 ## 1.00 8.38 5.29 ## 1.50 4.75 2.86 ## 2.00 3.34 2.01 ## 2.50 2.62 1.59 ## 3.00 2.19 1.32 ## 4.00 1.71 1.07 ## 5.00 1.31 1.01 ## Vance (1986), one-sided CUSUM ## The first paper on using Nystroem method and Gauss-Legendre quadrature ## for solving the ARL integral equation (see as well Goel/Wu, 1971) k <- 0 h <- 10 mu <- c(-.25,-.125,0,.125,.25,.5,.75,1) round(cbind(mu,sapply(mu,k=k,h=h,xcusum.arl)),digits=2) ## results in the original paper are (in Table 1 incl. Goel/Wu (1971) results) ## -0.25 2071.51 ## -0.125 400.28 ## 0.0 124.66 ## 0.125 59.30 ## 0.25 36.71 ## 0.50 20.37 ## 0.75 14.06 ## 1.00 10.75 ## Waldmann (1986), ## one- and two-sided CUSUM ## one-sided case k <- .5 h <- 3 mu <- c(-.5,0,.5) round(sapply(mu,k=k,h=h,xcusum.arl),digits=2) ## results in the original paper are 1963, 117.4, and 17.35, resp. ## (in Tables 3, 1, and 5, resp.). ## two-sided case k <- .6 h <- 3 round(xcusum.arl(k,h,-.2,sided="two"),digits=1) # fits to Waldmann's setup ## result in the original paper is 65.4 (in Table 6). ## Crosier (1986), Crosier's modified two-sided CUSUM ## He introduced the modification and evaluated it by means of ## Markov chain approximation k <- .5 h <- 3.73 mu <- c(0,.25,.5,.75,1,1.5,2,2.5,3,4,5) round(cbind(mu,sapply(mu,k=k,h=h,sided="Crosier",xcusum.arl)),digits=2) ## results in the original paper are (in Table 3) ## 0.00 168. ## 0.25 70.7 ## 0.50 25.1 ## 0.75 12.5 ## 1.00 7.92 ## 1.50 4.49 ## 2.00 3.17 ## 2.50 2.49 ## 3.00 2.09 ## 4.00 1.60 ## 5.00 1.22 ## SAS/QC manual 1999 ## one- and two-sided CUSUM schemes ## one-sided k <- .25 h <- 8 mu <- 2.5 print(xcusum.arl(k,h,mu),digits=12) print(xcusum.arl(k,h,mu,hs=.1),digits=12) ## original results are 4.1500836225 and 4.1061588131. ## two-sided print(xcusum.arl(k,h,mu,sided="two"),digits=12) ## original result is 4.1500826715.
## Brook/Evans (1972), one-sided CUSUM ## Their results are based on the less accurate Markov chain approach. k <- .5 h <- 3 round(c( xcusum.arl(k,h,0), xcusum.arl(k,h,1.5) ),digits=2) ## results in the original paper are L0 = 117.59, L1 = 3.75 (in Subsection 4.3). ## Lucas, Crosier (1982) ## (one- and) two-sided CUSUM with possible headstarts k <- .5 h <- 4 mu <- c(0,.25,.5,.75,1,1.5,2,2.5,3,4,5) arl1 <- sapply(mu,k=k,h=h,sided="two",xcusum.arl) arl2 <- sapply(mu,k=k,h=h,hs=h/2,sided="two",xcusum.arl) round(cbind(mu,arl1,arl2),digits=2) ## results in the original paper are (in Table 1) ## 0.00 168. 149. ## 0.25 74.2 62.7 ## 0.50 26.6 20.1 ## 0.75 13.3 8.97 ## 1.00 8.38 5.29 ## 1.50 4.75 2.86 ## 2.00 3.34 2.01 ## 2.50 2.62 1.59 ## 3.00 2.19 1.32 ## 4.00 1.71 1.07 ## 5.00 1.31 1.01 ## Vance (1986), one-sided CUSUM ## The first paper on using Nystroem method and Gauss-Legendre quadrature ## for solving the ARL integral equation (see as well Goel/Wu, 1971) k <- 0 h <- 10 mu <- c(-.25,-.125,0,.125,.25,.5,.75,1) round(cbind(mu,sapply(mu,k=k,h=h,xcusum.arl)),digits=2) ## results in the original paper are (in Table 1 incl. Goel/Wu (1971) results) ## -0.25 2071.51 ## -0.125 400.28 ## 0.0 124.66 ## 0.125 59.30 ## 0.25 36.71 ## 0.50 20.37 ## 0.75 14.06 ## 1.00 10.75 ## Waldmann (1986), ## one- and two-sided CUSUM ## one-sided case k <- .5 h <- 3 mu <- c(-.5,0,.5) round(sapply(mu,k=k,h=h,xcusum.arl),digits=2) ## results in the original paper are 1963, 117.4, and 17.35, resp. ## (in Tables 3, 1, and 5, resp.). ## two-sided case k <- .6 h <- 3 round(xcusum.arl(k,h,-.2,sided="two"),digits=1) # fits to Waldmann's setup ## result in the original paper is 65.4 (in Table 6). ## Crosier (1986), Crosier's modified two-sided CUSUM ## He introduced the modification and evaluated it by means of ## Markov chain approximation k <- .5 h <- 3.73 mu <- c(0,.25,.5,.75,1,1.5,2,2.5,3,4,5) round(cbind(mu,sapply(mu,k=k,h=h,sided="Crosier",xcusum.arl)),digits=2) ## results in the original paper are (in Table 3) ## 0.00 168. ## 0.25 70.7 ## 0.50 25.1 ## 0.75 12.5 ## 1.00 7.92 ## 1.50 4.49 ## 2.00 3.17 ## 2.50 2.49 ## 3.00 2.09 ## 4.00 1.60 ## 5.00 1.22 ## SAS/QC manual 1999 ## one- and two-sided CUSUM schemes ## one-sided k <- .25 h <- 8 mu <- 2.5 print(xcusum.arl(k,h,mu),digits=12) print(xcusum.arl(k,h,mu,hs=.1),digits=12) ## original results are 4.1500836225 and 4.1061588131. ## two-sided print(xcusum.arl(k,h,mu,sided="two"),digits=12) ## original result is 4.1500826715.
Computation of the decision intervals (alarm limits) for different types of CUSUM control charts monitoring normal mean.
xcusum.crit(k, L0, mu0 = 0, hs = 0, sided = "one", r = 30)
xcusum.crit(k, L0, mu0 = 0, hs = 0, sided = "one", r = 30)
k |
reference value of the CUSUM control chart. |
L0 |
in-control ARL. |
mu0 |
in-control mean. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one-, two-sided and Crosier's modified
two-sided CUSUM scheme by choosing |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
xcusum.crit
determines the decision interval (alarm limit)
for given in-control ARL L0
by applying secant rule and using xcusum.arl()
.
Returns a single value which resembles the decision interval
h
.
Sven Knoth
xcusum.arl
for zero-state ARL computation.
k <- .5 incontrolARL <- c(500,5000,50000) sapply(incontrolARL,k=k,xcusum.crit,r=10) # accuracy with 10 nodes sapply(incontrolARL,k=k,xcusum.crit,r=20) # accuracy with 20 nodes sapply(incontrolARL,k=k,xcusum.crit) # accuracy with 30 nodes
k <- .5 incontrolARL <- c(500,5000,50000) sapply(incontrolARL,k=k,xcusum.crit,r=10) # accuracy with 10 nodes sapply(incontrolARL,k=k,xcusum.crit,r=20) # accuracy with 20 nodes sapply(incontrolARL,k=k,xcusum.crit) # accuracy with 30 nodes
Computation of the reference value k for one-sided CUSUM control charts monitoring normal mean, if the in-control ARL L0 and the alarm threshold h are given.
xcusum.crit.L0h(L0, h, hs=0, sided="one", r=30, L0.eps=1e-6, k.eps=1e-8)
xcusum.crit.L0h(L0, h, hs=0, sided="one", r=30, L0.eps=1e-6, k.eps=1e-8)
L0 |
in-control ARL. |
h |
alarm level of the CUSUM control chart. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one-, two-sided and Crosier's modified
two-sided CUSUM scheme choosing |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
L0.eps |
error bound for the L0 error. |
k.eps |
bound for the difference of two successive values of k. |
xcusum.crit.L0h
determines the reference value k
for given in-control ARL L0
and alarm level h
by applying secant rule and using xcusum.arl()
. Note that
not for any combination of L0
and h
a solution exists
– for given L0
there is a maximal value for h
to get a valid result k
.
Returns a single value which resembles the reference value k
.
Sven Knoth
xcusum.arl
for zero-state ARL computation.
L0 <- 100 h.max <- xcusum.crit(0, L0, 0) hs <- (300:1)/100 hs <- hs[hs < h.max] ks <- NULL for ( h in hs ) ks <- c(ks, xcusum.crit.L0h(L0, h)) k.max <- qnorm( 1 - 1/L0 ) plot(hs, ks, type="l", ylim=c(0, max(k.max, ks)), xlab="h", ylab="k") abline(h=c(0, k.max), col="red")
L0 <- 100 h.max <- xcusum.crit(0, L0, 0) hs <- (300:1)/100 hs <- hs[hs < h.max] ks <- NULL for ( h in hs ) ks <- c(ks, xcusum.crit.L0h(L0, h)) k.max <- qnorm( 1 - 1/L0 ) plot(hs, ks, type="l", ylim=c(0, max(k.max, ks)), xlab="h", ylab="k") abline(h=c(0, k.max), col="red")
Computation of the reference value k and the alarm threshold h for one-sided CUSUM control charts monitoring normal mean, if the in-control ARL L0 and the out-of-control L1 are given.
xcusum.crit.L0L1(L0, L1, hs=0, sided="one", r=30, L1.eps=1e-6, k.eps=1e-8)
xcusum.crit.L0L1(L0, L1, hs=0, sided="one", r=30, L1.eps=1e-6, k.eps=1e-8)
L0 |
in-control ARL. |
L1 |
out-of-control ARL. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one-, two-sided and Crosier's modified
two-sided CUSUM schemoosing |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
L1.eps |
error bound for the L1 error. |
k.eps |
bound for the difference of two successive values of k. |
xcusum.crit.L0L1
determines the reference value k and the alarm threshold h
for given in-control ARL L0
and out-of-control ARL L1
by applying secant rule and using xcusum.arl()
and xcusum.crit()
.
These CUSUM design rules were firstly (and quite rarely afterwards) used by Ewan and Kemp.
Returns two values which resemble the reference value k
and the threshold h
.
Sven Knoth
W. D. Ewan and K. W. Kemp (1960), Sampling inspection of continuous processes with no autocorrelation between successive results, Biometrika 47, 363-380.
K. W. Kemp (1962), The Use of Cumulative Sums for Sampling Inspection Schemes, Journal of the Royal Statistical Sociecty C, Applied Statistics, 10, 16-31.
xcusum.arl
for zero-state ARL and xcusum.crit
for threshold h computation.
## Table 2 from Ewan/Kemp (1960) -- one-sided CUSUM # # A.R.L. at A.Q.L. A.R.L. at A.Q.L. k h # 1000 3 1.12 2.40 # 1000 7 0.65 4.06 # 500 3 1.04 2.26 # 500 7 0.60 3.80 # 250 3 0.94 2.11 # 250 7 0.54 3.51 # L0.set <- c(1000, 500, 250) L1.set <- c(3, 7) cat("\nL0\tL1\tk\th\n") for ( L0 in L0.set ) { for ( L1 in L1.set ) { result <- round(xcusum.crit.L0L1(L0, L1), digits=2) cat(paste(L0, L1, result[1], result[2], sep="\t"), "\n") } } # # two confirmation runs xcusum.arl(0.54, 3.51, 0) # Ewan/Kemp xcusum.arl(result[1], result[2], 0) # here xcusum.arl(0.54, 3.51, 2*0.54) # Ewan/Kemp xcusum.arl(result[1], result[2], 2*result[1]) # here # ## Table II from Kemp (1962) -- two-sided CUSUM # # Lr k # La=250 La=500 La=1000 # 2.5 1.05 1.17 1.27 # 3.0 0.94 1.035 1.13 # 4.0 0.78 0.85 0.92 # 5.0 0.68 0.74 0.80 # 6.0 0.60 0.655 0.71 # 7.5 0.52 0.57 0.62 # 10.0 0.43 0.48 0.52 # L0.set <- c(250, 500, 1000) L1.set <- c(2.5, 3:6, 7.5, 10) cat("\nL1\tL0=250\tL0=500\tL0=1000\n") for ( L1 in L1.set ) { cat(L1) for ( L0 in L0.set ) { result <- round(xcusum.crit.L0L1(L0, L1, sided="two"), digits=2) cat("\t", result[1]) } cat("\n") }
## Table 2 from Ewan/Kemp (1960) -- one-sided CUSUM # # A.R.L. at A.Q.L. A.R.L. at A.Q.L. k h # 1000 3 1.12 2.40 # 1000 7 0.65 4.06 # 500 3 1.04 2.26 # 500 7 0.60 3.80 # 250 3 0.94 2.11 # 250 7 0.54 3.51 # L0.set <- c(1000, 500, 250) L1.set <- c(3, 7) cat("\nL0\tL1\tk\th\n") for ( L0 in L0.set ) { for ( L1 in L1.set ) { result <- round(xcusum.crit.L0L1(L0, L1), digits=2) cat(paste(L0, L1, result[1], result[2], sep="\t"), "\n") } } # # two confirmation runs xcusum.arl(0.54, 3.51, 0) # Ewan/Kemp xcusum.arl(result[1], result[2], 0) # here xcusum.arl(0.54, 3.51, 2*0.54) # Ewan/Kemp xcusum.arl(result[1], result[2], 2*result[1]) # here # ## Table II from Kemp (1962) -- two-sided CUSUM # # Lr k # La=250 La=500 La=1000 # 2.5 1.05 1.17 1.27 # 3.0 0.94 1.035 1.13 # 4.0 0.78 0.85 0.92 # 5.0 0.68 0.74 0.80 # 6.0 0.60 0.655 0.71 # 7.5 0.52 0.57 0.62 # 10.0 0.43 0.48 0.52 # L0.set <- c(250, 500, 1000) L1.set <- c(2.5, 3:6, 7.5, 10) cat("\nL1\tL0=250\tL0=500\tL0=1000\n") for ( L1 in L1.set ) { cat(L1) for ( L0 in L0.set ) { result <- round(xcusum.crit.L0L1(L0, L1, sided="two"), digits=2) cat("\t", result[1]) } cat("\n") }
Computation of quantiles of the Run Length (RL)for CUSUM control charts monitoring normal mean.
xcusum.q(k, h, mu, alpha, hs=0, sided="one", r=40)
xcusum.q(k, h, mu, alpha, hs=0, sided="one", r=40)
k |
reference value of the CUSUM control chart. |
h |
decision interval (alarm limit, threshold) of the CUSUM control chart. |
mu |
true mean. |
alpha |
quantile level. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided CUSUM control chart by choosing |
r |
number of quadrature nodes, dimension of the resulting linear equation system is equal to |
Instead of the popular ARL (Average Run Length) quantiles of the CUSUM stopping time (Run Length) are determined. The algorithm is based on Waldmann's survival function iteration procedure.
Returns a single value which resembles the RL quantile of order q
.
Sven Knoth
K.-H. Waldmann (1986), Bounds for the distribution of the run length of one-sided and two-sided CUSUM quality control schemes, Technometrics 28, 61-67.
xcusum.arl
for zero-state ARL computation of CUSUM control charts.
## Waldmann (1986), one-sided CUSUM, Table 2 ## original values are 345, 82, 9 XCUSUM.Q <- Vectorize("xcusum.q", "alpha") k <- .5 h <- 3 mu <- 0 # corresponds to Waldmann's -0.5 a.list <- c(.95, .5, .05) rl.quantiles <- ceiling(XCUSUM.Q(k, h, mu, a.list)) cbind(a.list, rl.quantiles)
## Waldmann (1986), one-sided CUSUM, Table 2 ## original values are 345, 82, 9 XCUSUM.Q <- Vectorize("xcusum.q", "alpha") k <- .5 h <- 3 mu <- 0 # corresponds to Waldmann's -0.5 a.list <- c(.95, .5, .05) rl.quantiles <- ceiling(XCUSUM.Q(k, h, mu, a.list)) cbind(a.list, rl.quantiles)
Computation of the survival function of the Run Length (RL) for CUSUM control charts monitoring normal mean.
xcusum.sf(k, h, mu, n, hs=0, sided="one", r=40)
xcusum.sf(k, h, mu, n, hs=0, sided="one", r=40)
k |
reference value of the CUSUM control chart. |
h |
decision interval (alarm limit, threshold) of the CUSUM control chart. |
mu |
true mean. |
n |
calculate sf up to value |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided CUSUM control chart by choosing |
r |
number of quadrature nodes, dimension of the resulting linear equation system is equal to |
The survival function P(L>n) and derived from it also the cdf P(L<=n) and the pmf P(L=n) illustrate the distribution of the CUSUM run length. For large n the geometric tail could be exploited. That is, with reasonable large n the complete distribution is characterized. The algorithm is based on Waldmann's survival function iteration procedure.
Returns a vector which resembles the survival function up to a certain point.
Sven Knoth
K.-H. Waldmann (1986), Bounds for the distribution of the run length of one-sided and two-sided CUSUM quality control schemes, Technometrics 28, 61-67.
xcusum.q
for computation of CUSUM run length quantiles.
## Waldmann (1986), one-sided CUSUM, Table 2 k <- .5 h <- 3 mu <- 0 # corresponds to Waldmann's -0.5 SF <- xcusum.sf(k, h, 0, 1000) plot(1:length(SF), SF, type="l", xlab="n", ylab="P(L>n)", ylim=c(0,1)) #
## Waldmann (1986), one-sided CUSUM, Table 2 k <- .5 h <- 3 mu <- 0 # corresponds to Waldmann's -0.5 SF <- xcusum.sf(k, h, 0, 1000) plot(1:length(SF), SF, type="l", xlab="n", ylab="P(L>n)", ylim=c(0,1)) #
Computation of the (zero-state and other) Average Run Length (ARL) under drift for one-sided CUSUM control charts monitoring normal mean.
xDcusum.arl(k, h, delta, hs = 0, sided = "one", mode = "Gan", m = NULL, q = 1, r = 30, with0 = FALSE)
xDcusum.arl(k, h, delta, hs = 0, sided = "one", mode = "Gan", m = NULL, q = 1, r = 30, with0 = FALSE)
k |
reference value of the CUSUM control chart. |
h |
decision interval (alarm limit, threshold) of the CUSUM control chart. |
delta |
true drift parameter. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided CUSUM control chart
by choosing |
mode |
decide whether Gan's or Knoth's approach is used. Use
|
m |
parameter used if |
q |
change point position. For |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
with0 |
defines whether the first observation used for the RL
calculation follows already 1*delta or still 0*delta.
With |
Based on Gan (1991) or Knoth (2003), the ARL is calculated for one-sided CUSUM control charts under drift. In case of Gan's framework, the usual ARL function with mu=m*delta is determined and recursively via m-1, m-2, ... 1 (or 0) the drift ARL determined. The framework of Knoth allows to calculate ARLs for varying parameters, such as control limits and distributional parameters. For details see the cited papers. Note that two-sided CUSUM charts under drift are difficult to treat.
Returns a single value which resembles the ARL.
Sven Knoth
F. F. Gan (1992), CUSUM control charts under linear drift, Statistician 41, 71-84.
F. F. Gan (1996), Average Run Lengths for Cumulative Sum control chart under linear trend, Applied Statistics 45, 505-512.
S. Knoth (2003), EWMA schemes with non-homogeneous transition kernels, Sequential Analysis 22, 241-255.
S. Knoth (2012), More on Control Charting under Drift, in: Frontiers in Statistical Quality Control 10, H.-J. Lenz, W. Schmid and P.-T. Wilrich (Eds.), Physica Verlag, Heidelberg, Germany, 53-68.
C. Zou, Y. Liu and Z. Wang (2009), Comparisons of control schemes for monitoring the means of processes subject to drifts, Metrika 70, 141-163.
xcusum.arl
and xcusum.ad
for zero-state and
steady-state ARL computation of CUSUM control charts
for the classical step change model.
## Gan (1992) ## Table 1 ## original values are # deltas arl # 0.0001 475 # 0.0005 261 # 0.0010 187 # 0.0020 129 # 0.0050 76.3 # 0.0100 52.0 # 0.0200 35.2 # 0.0500 21.4 # 0.1000 15.0 # 0.5000 6.95 # 1.0000 5.16 # 3.0000 3.30 ## Not run: k <- .25 h <- 8 r <- 50 DxDcusum.arl <- Vectorize(xDcusum.arl, "delta") deltas <- c(0.0001, 0.0005, 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.5, 1, 3) arl.like.Gan <- round(DxDcusum.arl(k, h, deltas, r=r, with0=TRUE), digits=2) arl.like.Knoth <- round(DxDcusum.arl(k, h, deltas, r=r, mode="Knoth", with0=TRUE), digits=2) data.frame(deltas, arl.like.Gan, arl.like.Knoth) ## End(Not run) ## Zou et al. (2009) ## Table 1 ## original values are # delta arl1 arl2 arl3 # 0 ~ 1730 # 0.0005 345 412 470 # 0.001 231 275 317 # 0.005 86.6 98.6 112 # 0.01 56.9 61.8 69.3 # 0.05 22.6 21.6 22.7 # 0.1 15.4 14.7 14.2 # 0.5 6.60 5.54 5.17 # 1.0 4.63 3.80 3.45 # 2.0 3.17 2.67 2.32 # 3.0 2.79 2.04 1.96 # 4.0 2.10 1.98 1.74 ## Not run: k1 <- 0.25 k2 <- 0.5 k3 <- 0.75 h1 <- 9.660 h2 <- 5.620 h3 <- 3.904 deltas <- c(0.0005, 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1:4) arl1 <- c(round(xcusum.arl(k1, h1, 0, r=r), digits=2), round(DxDcusum.arl(k1, h1, deltas, r=r), digits=2)) arl2 <- c(round(xcusum.arl(k2, h2, 0), digits=2), round(DxDcusum.arl(k2, h2, deltas, r=r), digits=2)) arl3 <- c(round(xcusum.arl(k3, h3, 0, r=r), digits=2), round(DxDcusum.arl(k3, h3, deltas, r=r), digits=2)) data.frame(delta=c(0, deltas), arl1, arl2, arl3) ## End(Not run)
## Gan (1992) ## Table 1 ## original values are # deltas arl # 0.0001 475 # 0.0005 261 # 0.0010 187 # 0.0020 129 # 0.0050 76.3 # 0.0100 52.0 # 0.0200 35.2 # 0.0500 21.4 # 0.1000 15.0 # 0.5000 6.95 # 1.0000 5.16 # 3.0000 3.30 ## Not run: k <- .25 h <- 8 r <- 50 DxDcusum.arl <- Vectorize(xDcusum.arl, "delta") deltas <- c(0.0001, 0.0005, 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.5, 1, 3) arl.like.Gan <- round(DxDcusum.arl(k, h, deltas, r=r, with0=TRUE), digits=2) arl.like.Knoth <- round(DxDcusum.arl(k, h, deltas, r=r, mode="Knoth", with0=TRUE), digits=2) data.frame(deltas, arl.like.Gan, arl.like.Knoth) ## End(Not run) ## Zou et al. (2009) ## Table 1 ## original values are # delta arl1 arl2 arl3 # 0 ~ 1730 # 0.0005 345 412 470 # 0.001 231 275 317 # 0.005 86.6 98.6 112 # 0.01 56.9 61.8 69.3 # 0.05 22.6 21.6 22.7 # 0.1 15.4 14.7 14.2 # 0.5 6.60 5.54 5.17 # 1.0 4.63 3.80 3.45 # 2.0 3.17 2.67 2.32 # 3.0 2.79 2.04 1.96 # 4.0 2.10 1.98 1.74 ## Not run: k1 <- 0.25 k2 <- 0.5 k3 <- 0.75 h1 <- 9.660 h2 <- 5.620 h3 <- 3.904 deltas <- c(0.0005, 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1:4) arl1 <- c(round(xcusum.arl(k1, h1, 0, r=r), digits=2), round(DxDcusum.arl(k1, h1, deltas, r=r), digits=2)) arl2 <- c(round(xcusum.arl(k2, h2, 0), digits=2), round(DxDcusum.arl(k2, h2, deltas, r=r), digits=2)) arl3 <- c(round(xcusum.arl(k3, h3, 0, r=r), digits=2), round(DxDcusum.arl(k3, h3, deltas, r=r), digits=2)) data.frame(delta=c(0, deltas), arl1, arl2, arl3) ## End(Not run)
Computation of the (zero-state and other) Average Run Length (ARL) under drift for different types of EWMA control charts monitoring normal mean.
xDewma.arl(l, c, delta, zr = 0, hs = 0, sided = "one", limits = "fix", mode = "Gan", m = NULL, q = 1, r = 40, with0 = FALSE)
xDewma.arl(l, c, delta, zr = 0, hs = 0, sided = "one", limits = "fix", mode = "Gan", m = NULL, q = 1, r = 40, with0 = FALSE)
l |
smoothing parameter lambda of the EWMA control chart. |
c |
critical value (similar to alarm limit) of the EWMA control chart. |
delta |
true drift parameter. |
zr |
reflection border for the one-sided chart. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguish between one- and two-sided EWMA control chart
by choosing |
limits |
distinguishes between different control limits behavior. |
mode |
decide whether Gan's or Knoth's approach is used. Use
|
m |
parameter used if |
q |
change point position. For |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
with0 |
defines whether the first observation used for the RL calculation
follows already 1*delta or still 0*delta.
With |
Based on Gan (1991) or Knoth (2003), the ARL is calculated for EWMA control charts under drift. In case of Gan's framework, the usual ARL function with mu=m*delta is determined and recursively via m-1, m-2, ... 1 (or 0) the drift ARL determined. The framework of Knoth allows to calculate ARLs for varying parameters, such as control limits and distributional parameters. For details see the cited papers.
Returns a single value which resembles the ARL.
Sven Knoth
F. F. Gan (1991), EWMA control chart under linear drift, J. Stat. Comput. Simulation 38, 181-200.
L. A. Aerne, C. W. Champ and S. E. Rigdon (1991), Evaluation of control charts under linear trend, Commun. Stat., Theory Methods 20, 3341-3349.
S. Knoth (2003), EWMA schemes with non-homogeneous transition kernels, Sequential Analysis 22, 241-255.
H. M. Fahmy and E. A. Elsayed (2006), Detection of linear trends in process mean, International Journal of Production Research 44, 487-504.
S. Knoth (2012), More on Control Charting under Drift, in: Frontiers in Statistical Quality Control 10, H.-J. Lenz, W. Schmid and P.-T. Wilrich (Eds.), Physica Verlag, Heidelberg, Germany, 53-68.
C. Zou, Y. Liu and Z. Wang (2009), Comparisons of control schemes for monitoring the means of processes subject to drifts, Metrika 70, 141-163.
xewma.arl
and xewma.ad
for zero-state and
steady-state ARL computation of EWMA control charts
for the classical step change model.
## Not run: DxDewma.arl <- Vectorize(xDewma.arl, "delta") ## Gan (1991) ## Table 1 ## original values are # delta arlE1 arlE2 arlE3 # 0 500 500 500 # 0.0001 482 460 424 # 0.0010 289 231 185 # 0.0020 210 162 129 # 0.0050 126 94.6 77.9 # 0.0100 81.7 61.3 52.7 # 0.0500 27.5 21.8 21.9 # 0.1000 17.0 14.2 15.3 # 1.0000 4.09 4.28 5.25 # 3.0000 2.60 2.90 3.43 # lambda1 <- 0.676 lambda2 <- 0.242 lambda3 <- 0.047 h1 <- 2.204/sqrt(lambda1/(2-lambda1)) h2 <- 1.111/sqrt(lambda2/(2-lambda2)) h3 <- 0.403/sqrt(lambda3/(2-lambda3)) deltas <- c(.0001, .001, .002, .005, .01, .05, .1, 1, 3) arlE10 <- round(xewma.arl(lambda1, h1, 0, sided="two"), digits=2) arlE1 <- c(arlE10, round(DxDewma.arl(lambda1, h1, deltas, sided="two", with0=TRUE), digits=2)) arlE20 <- round(xewma.arl(lambda2, h2, 0, sided="two"), digits=2) arlE2 <- c(arlE20, round(DxDewma.arl(lambda2, h2, deltas, sided="two", with0=TRUE), digits=2)) arlE30 <- round(xewma.arl(lambda3, h3, 0, sided="two"), digits=2) arlE3 <- c(arlE30, round(DxDewma.arl(lambda3, h3, deltas, sided="two", with0=TRUE), digits=2)) data.frame(delta=c(0, deltas), arlE1, arlE2, arlE3) ## do the same with more digits for the alarm threshold L0 <- 500 h1 <- xewma.crit(lambda1, L0, sided="two") h2 <- xewma.crit(lambda2, L0, sided="two") h3 <- xewma.crit(lambda3, L0, sided="two") lambdas <- c(lambda1, lambda2, lambda3) hs <- c(h1, h2, h3) * sqrt(lambdas/(2-lambdas)) hs # compare with Gan's values 2.204, 1.111, 0.403 round(hs, digits=3) arlE10 <- round(xewma.arl(lambda1, h1, 0, sided="two"), digits=2) arlE1 <- c(arlE10, round(DxDewma.arl(lambda1, h1, deltas, sided="two", with0=TRUE), digits=2)) arlE20 <- round(xewma.arl(lambda2, h2, 0, sided="two"), digits=2) arlE2 <- c(arlE20, round(DxDewma.arl(lambda2, h2, deltas, sided="two", with0=TRUE), digits=2)) arlE30 <- round(xewma.arl(lambda3, h3, 0, sided="two"), digits=2) arlE3 <- c(arlE30, round(DxDewma.arl(lambda3, h3, deltas, sided="two", with0=TRUE), digits=2)) data.frame(delta=c(0, deltas), arlE1, arlE2, arlE3) ## Aerne et al. (1991) -- two-sided EWMA ## Table I (continued) ## original numbers are # delta arlE1 arlE2 arlE3 # 0.000000 465.0 465.0 465.0 # 0.005623 77.01 85.93 102.68 # 0.007499 64.61 71.78 85.74 # 0.010000 54.20 59.74 71.22 # 0.013335 45.20 49.58 58.90 # 0.017783 37.76 41.06 48.54 # 0.023714 31.54 33.95 39.87 # 0.031623 26.36 28.06 32.68 # 0.042170 22.06 23.19 26.73 # 0.056234 18.49 19.17 21.84 # 0.074989 15.53 15.87 17.83 # 0.100000 13.07 13.16 14.55 # 0.133352 11.03 10.94 11.88 # 0.177828 9.33 9.12 9.71 # 0.237137 7.91 7.62 7.95 # 0.316228 6.72 6.39 6.52 # 0.421697 5.72 5.38 5.37 # 0.562341 4.88 4.54 4.44 # 0.749894 4.18 3.84 3.68 # 1.000000 3.58 3.27 3.07 # lambda1 <- .133 lambda2 <- .25 lambda3 <- .5 cE1 <- 2.856 cE2 <- 2.974 cE3 <- 3.049 deltas <- 10^(-(18:0)/8) arlE10 <- round(xewma.arl(lambda1, cE1, 0, sided="two"), digits=2) arlE1 <- c(arlE10, round(DxDewma.arl(lambda1, cE1, deltas, sided="two"), digits=2)) arlE20 <- round(xewma.arl(lambda2, cE2, 0, sided="two"), digits=2) arlE2 <- c(arlE20, round(DxDewma.arl(lambda2, cE2, deltas, sided="two"), digits=2)) arlE30 <- round(xewma.arl(lambda3, cE3, 0, sided="two"), digits=2) arlE3 <- c(arlE30, round(DxDewma.arl(lambda3, cE3, deltas, sided="two"), digits=2)) data.frame(delta=c(0, round(deltas, digits=6)), arlE1, arlE2, arlE3) ## Fahmy/Elsayed (2006) -- two-sided EWMA ## Table 4 (Monte Carlo results, 10^4 replicates, change point at t=51!) ## original numbers are # delta arl s.e. # 0.00 365.749 3.598 # 0.10 12.971 0.029 # 0.25 7.738 0.015 # 0.50 5.312 0.009 # 0.75 4.279 0.007 # 1.00 3.680 0.006 # 1.25 3.271 0.006 # 1.50 2.979 0.005 # 1.75 2.782 0.004 # 2.00 2.598 0.005 # lambda <- 0.1 cE <- 2.7 deltas <- c(.1, (1:8)/4) arlE1 <- c(round(xewma.arl(lambda, cE, 0, sided="two"), digits=3), round(DxDewma.arl(lambda, cE, deltas, sided="two"), digits=3)) arlE51 <- c(round(xewma.arl(lambda, cE, 0, sided="two", q=51)[51], digits=3), round(DxDewma.arl(lambda, cE, deltas, sided="two", mode="Knoth", q=51), digits=3)) data.frame(delta=c(0, deltas), arlE1, arlE51) ## additional Monte Carlo results with 10^8 replicates # delta arl.q=1 s.e. arl.q=51 s.e. # 0.00 368.910 0.036 361.714 0.038 # 0.10 12.986 0.000 12.781 0.000 # 0.25 7.758 0.000 7.637 0.000 # 0.50 5.318 0.000 5.235 0.000 # 0.75 4.285 0.000 4.218 0.000 # 1.00 3.688 0.000 3.628 0.000 # 1.25 3.274 0.000 3.233 0.000 # 1.50 2.993 0.000 2.942 0.000 # 1.75 2.808 0.000 2.723 0.000 # 2.00 2.616 0.000 2.554 0.000 ## Zou et al. (2009) -- one-sided EWMA ## Table 1 ## original values are # delta arl1 arl2 arl3 # 0 ~ 1730 # 0.0005 317 377 440 # 0.001 215 253 297 # 0.005 83.6 92.6 106 # 0.01 55.6 58.8 66.1 # 0.05 22.6 21.1 22.0 # 0.1 15.5 13.9 13.8 # 0.5 6.65 5.56 5.09 # 1.0 4.67 3.83 3.43 # 2.0 3.21 2.74 2.32 # 3.0 2.86 2.06 1.98 # 4.0 2.14 2.00 1.83 l1 <- 0.03479 l2 <- 0.11125 l3 <- 0.23052 c1 <- 2.711 c2 <- 3.033 c3 <- 3.161 zr <- -6 r <- 50 deltas <- c(0.0005, 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1:4) arl1 <- c(round(xewma.arl(l1, c1, 0, zr=zr, r=r), digits=2), round(DxDewma.arl(l1, c1, deltas, zr=zr, r=r), digits=2)) arl2 <- c(round(xewma.arl(l2, c2, 0, zr=zr), digits=2), round(DxDewma.arl(l2, c2, deltas, zr=zr, r=r), digits=2)) arl3 <- c(round(xewma.arl(l3, c3, 0, zr=zr, r=r), digits=2), round(DxDewma.arl(l3, c3, deltas, zr=zr, r=r), digits=2)) data.frame(delta=c(0, deltas), arl1, arl2, arl3) ## End(Not run)
## Not run: DxDewma.arl <- Vectorize(xDewma.arl, "delta") ## Gan (1991) ## Table 1 ## original values are # delta arlE1 arlE2 arlE3 # 0 500 500 500 # 0.0001 482 460 424 # 0.0010 289 231 185 # 0.0020 210 162 129 # 0.0050 126 94.6 77.9 # 0.0100 81.7 61.3 52.7 # 0.0500 27.5 21.8 21.9 # 0.1000 17.0 14.2 15.3 # 1.0000 4.09 4.28 5.25 # 3.0000 2.60 2.90 3.43 # lambda1 <- 0.676 lambda2 <- 0.242 lambda3 <- 0.047 h1 <- 2.204/sqrt(lambda1/(2-lambda1)) h2 <- 1.111/sqrt(lambda2/(2-lambda2)) h3 <- 0.403/sqrt(lambda3/(2-lambda3)) deltas <- c(.0001, .001, .002, .005, .01, .05, .1, 1, 3) arlE10 <- round(xewma.arl(lambda1, h1, 0, sided="two"), digits=2) arlE1 <- c(arlE10, round(DxDewma.arl(lambda1, h1, deltas, sided="two", with0=TRUE), digits=2)) arlE20 <- round(xewma.arl(lambda2, h2, 0, sided="two"), digits=2) arlE2 <- c(arlE20, round(DxDewma.arl(lambda2, h2, deltas, sided="two", with0=TRUE), digits=2)) arlE30 <- round(xewma.arl(lambda3, h3, 0, sided="two"), digits=2) arlE3 <- c(arlE30, round(DxDewma.arl(lambda3, h3, deltas, sided="two", with0=TRUE), digits=2)) data.frame(delta=c(0, deltas), arlE1, arlE2, arlE3) ## do the same with more digits for the alarm threshold L0 <- 500 h1 <- xewma.crit(lambda1, L0, sided="two") h2 <- xewma.crit(lambda2, L0, sided="two") h3 <- xewma.crit(lambda3, L0, sided="two") lambdas <- c(lambda1, lambda2, lambda3) hs <- c(h1, h2, h3) * sqrt(lambdas/(2-lambdas)) hs # compare with Gan's values 2.204, 1.111, 0.403 round(hs, digits=3) arlE10 <- round(xewma.arl(lambda1, h1, 0, sided="two"), digits=2) arlE1 <- c(arlE10, round(DxDewma.arl(lambda1, h1, deltas, sided="two", with0=TRUE), digits=2)) arlE20 <- round(xewma.arl(lambda2, h2, 0, sided="two"), digits=2) arlE2 <- c(arlE20, round(DxDewma.arl(lambda2, h2, deltas, sided="two", with0=TRUE), digits=2)) arlE30 <- round(xewma.arl(lambda3, h3, 0, sided="two"), digits=2) arlE3 <- c(arlE30, round(DxDewma.arl(lambda3, h3, deltas, sided="two", with0=TRUE), digits=2)) data.frame(delta=c(0, deltas), arlE1, arlE2, arlE3) ## Aerne et al. (1991) -- two-sided EWMA ## Table I (continued) ## original numbers are # delta arlE1 arlE2 arlE3 # 0.000000 465.0 465.0 465.0 # 0.005623 77.01 85.93 102.68 # 0.007499 64.61 71.78 85.74 # 0.010000 54.20 59.74 71.22 # 0.013335 45.20 49.58 58.90 # 0.017783 37.76 41.06 48.54 # 0.023714 31.54 33.95 39.87 # 0.031623 26.36 28.06 32.68 # 0.042170 22.06 23.19 26.73 # 0.056234 18.49 19.17 21.84 # 0.074989 15.53 15.87 17.83 # 0.100000 13.07 13.16 14.55 # 0.133352 11.03 10.94 11.88 # 0.177828 9.33 9.12 9.71 # 0.237137 7.91 7.62 7.95 # 0.316228 6.72 6.39 6.52 # 0.421697 5.72 5.38 5.37 # 0.562341 4.88 4.54 4.44 # 0.749894 4.18 3.84 3.68 # 1.000000 3.58 3.27 3.07 # lambda1 <- .133 lambda2 <- .25 lambda3 <- .5 cE1 <- 2.856 cE2 <- 2.974 cE3 <- 3.049 deltas <- 10^(-(18:0)/8) arlE10 <- round(xewma.arl(lambda1, cE1, 0, sided="two"), digits=2) arlE1 <- c(arlE10, round(DxDewma.arl(lambda1, cE1, deltas, sided="two"), digits=2)) arlE20 <- round(xewma.arl(lambda2, cE2, 0, sided="two"), digits=2) arlE2 <- c(arlE20, round(DxDewma.arl(lambda2, cE2, deltas, sided="two"), digits=2)) arlE30 <- round(xewma.arl(lambda3, cE3, 0, sided="two"), digits=2) arlE3 <- c(arlE30, round(DxDewma.arl(lambda3, cE3, deltas, sided="two"), digits=2)) data.frame(delta=c(0, round(deltas, digits=6)), arlE1, arlE2, arlE3) ## Fahmy/Elsayed (2006) -- two-sided EWMA ## Table 4 (Monte Carlo results, 10^4 replicates, change point at t=51!) ## original numbers are # delta arl s.e. # 0.00 365.749 3.598 # 0.10 12.971 0.029 # 0.25 7.738 0.015 # 0.50 5.312 0.009 # 0.75 4.279 0.007 # 1.00 3.680 0.006 # 1.25 3.271 0.006 # 1.50 2.979 0.005 # 1.75 2.782 0.004 # 2.00 2.598 0.005 # lambda <- 0.1 cE <- 2.7 deltas <- c(.1, (1:8)/4) arlE1 <- c(round(xewma.arl(lambda, cE, 0, sided="two"), digits=3), round(DxDewma.arl(lambda, cE, deltas, sided="two"), digits=3)) arlE51 <- c(round(xewma.arl(lambda, cE, 0, sided="two", q=51)[51], digits=3), round(DxDewma.arl(lambda, cE, deltas, sided="two", mode="Knoth", q=51), digits=3)) data.frame(delta=c(0, deltas), arlE1, arlE51) ## additional Monte Carlo results with 10^8 replicates # delta arl.q=1 s.e. arl.q=51 s.e. # 0.00 368.910 0.036 361.714 0.038 # 0.10 12.986 0.000 12.781 0.000 # 0.25 7.758 0.000 7.637 0.000 # 0.50 5.318 0.000 5.235 0.000 # 0.75 4.285 0.000 4.218 0.000 # 1.00 3.688 0.000 3.628 0.000 # 1.25 3.274 0.000 3.233 0.000 # 1.50 2.993 0.000 2.942 0.000 # 1.75 2.808 0.000 2.723 0.000 # 2.00 2.616 0.000 2.554 0.000 ## Zou et al. (2009) -- one-sided EWMA ## Table 1 ## original values are # delta arl1 arl2 arl3 # 0 ~ 1730 # 0.0005 317 377 440 # 0.001 215 253 297 # 0.005 83.6 92.6 106 # 0.01 55.6 58.8 66.1 # 0.05 22.6 21.1 22.0 # 0.1 15.5 13.9 13.8 # 0.5 6.65 5.56 5.09 # 1.0 4.67 3.83 3.43 # 2.0 3.21 2.74 2.32 # 3.0 2.86 2.06 1.98 # 4.0 2.14 2.00 1.83 l1 <- 0.03479 l2 <- 0.11125 l3 <- 0.23052 c1 <- 2.711 c2 <- 3.033 c3 <- 3.161 zr <- -6 r <- 50 deltas <- c(0.0005, 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1:4) arl1 <- c(round(xewma.arl(l1, c1, 0, zr=zr, r=r), digits=2), round(DxDewma.arl(l1, c1, deltas, zr=zr, r=r), digits=2)) arl2 <- c(round(xewma.arl(l2, c2, 0, zr=zr), digits=2), round(DxDewma.arl(l2, c2, deltas, zr=zr, r=r), digits=2)) arl3 <- c(round(xewma.arl(l3, c3, 0, zr=zr, r=r), digits=2), round(DxDewma.arl(l3, c3, deltas, zr=zr, r=r), digits=2)) data.frame(delta=c(0, deltas), arl1, arl2, arl3) ## End(Not run)
Computation of the (zero-state and other) Average Run Length (ARL) under drift for Shiryaev-Roberts schemes monitoring normal mean.
xDgrsr.arl(k, g, delta, zr = 0, hs = NULL, sided = "one", m = NULL, mode = "Gan", q = 1, r = 30, with0 = FALSE)
xDgrsr.arl(k, g, delta, zr = 0, hs = NULL, sided = "one", m = NULL, mode = "Gan", q = 1, r = 30, with0 = FALSE)
k |
reference value of the Shiryaev-Roberts scheme. |
g |
control limit (alarm threshold) of Shiryaev-Roberts scheme. |
delta |
true drift parameter. |
zr |
reflection border for the one-sided chart. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided
Shiryaev-Roberts schemes
by choosing |
m |
parameter used if |
q |
change point position. For |
mode |
decide whether Gan's or Knoth's approach is used. Use
|
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
with0 |
defines whether the first observation used for the RL calculation
follows already 1*delta or still 0*delta.
With |
Based on Gan (1991) or Knoth (2003), the ARL is calculated for Shiryaev-Roberts schemes under drift. In case of Gan's framework, the usual ARL function with mu=m*delta is determined and recursively via m-1, m-2, ... 1 (or 0) the drift ARL determined. The framework of Knoth allows to calculate ARLs for varying parameters, such as control limits and distributional parameters. For details see the cited papers.
Returns a single value which resembles the ARL.
Sven Knoth
F. F. Gan (1991), EWMA control chart under linear drift, J. Stat. Comput. Simulation 38, 181-200.
S. Knoth (2003), EWMA schemes with non-homogeneous transition kernels, Sequential Analysis 22, 241-255.
S. Knoth (2012), More on Control Charting under Drift, in: Frontiers in Statistical Quality Control 10, H.-J. Lenz, W. Schmid and P.-T. Wilrich (Eds.), Physica Verlag, Heidelberg, Germany, 53-68.
C. Zou, Y. Liu and Z. Wang (2009), Comparisons of control schemes for monitoring the means of processes subject to drifts, Metrika 70, 141-163.
xewma.arl
and xewma.ad
for zero-state and
steady-state ARL computation of EWMA control charts
for the classical step change model.
## Not run: ## Monte Carlo example with 10^8 replicates # delta arl s.e. # 0.0001 381.8240 0.0304 # 0.0005 238.4630 0.0148 # 0.001 177.4061 0.0097 # 0.002 125.9055 0.0061 # 0.005 75.7574 0.0031 # 0.01 50.2203 0.0018 # 0.02 32.9458 0.0011 # 0.05 18.9213 0.0005 # 0.1 12.6054 0.0003 # 0.5 5.2157 0.0001 # 1 3.6537 0.0001 # 3 2.0289 0.0000 k <- .5 L0 <- 500 zr <- -7 r <- 50 g <- xgrsr.crit(k, L0, zr=zr, r=r) DxDgrsr.arl <- Vectorize(xDgrsr.arl, "delta") deltas <- c(0.0001, 0.0005, 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.5, 1, 3) arls <- round(DxDgrsr.arl(k, g, deltas, zr=zr, r=r), digits=4) data.frame(deltas, arls) ## End(Not run)
## Not run: ## Monte Carlo example with 10^8 replicates # delta arl s.e. # 0.0001 381.8240 0.0304 # 0.0005 238.4630 0.0148 # 0.001 177.4061 0.0097 # 0.002 125.9055 0.0061 # 0.005 75.7574 0.0031 # 0.01 50.2203 0.0018 # 0.02 32.9458 0.0011 # 0.05 18.9213 0.0005 # 0.1 12.6054 0.0003 # 0.5 5.2157 0.0001 # 1 3.6537 0.0001 # 3 2.0289 0.0000 k <- .5 L0 <- 500 zr <- -7 r <- 50 g <- xgrsr.crit(k, L0, zr=zr, r=r) DxDgrsr.arl <- Vectorize(xDgrsr.arl, "delta") deltas <- c(0.0001, 0.0005, 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.5, 1, 3) arls <- round(DxDgrsr.arl(k, g, deltas, zr=zr, r=r), digits=4) data.frame(deltas, arls) ## End(Not run)
Computation of the zero-state Average Run Length (ARL) under drift for Shewhart control charts with and without runs rules monitoring normal mean.
xDshewhartrunsrules.arl(delta, c = 1, m = NULL, type = "12") xDshewhartrunsrulesFixedm.arl(delta, c = 1, m = 100, type = "12")
xDshewhartrunsrules.arl(delta, c = 1, m = NULL, type = "12") xDshewhartrunsrulesFixedm.arl(delta, c = 1, m = 100, type = "12")
delta |
true drift parameter. |
c |
normalizing constant to ensure specific alarming behavior. |
type |
controls the type of Shewhart chart used, seed details section. |
m |
parameter of Gan's approach. If |
Based on Gan (1991), the ARL is calculated for
Shewhart control charts with and without runs rules
under drift. The usual ARL function with mu=m*delta is determined and recursively via
m-1, m-2, ... 1 (or 0) the drift ARL determined.
xDshewhartrunsrulesFixedm.arl
is the actual work horse, while
xDshewhartrunsrules.arl
provides a convenience wrapper.
Note that Aerne et al. (1991) deployed a method that is
quite similar to Gan's algorithm. For type
see
the help page of xshewhartrunsrules.arl
.
Returns a single value which resembles the ARL.
Sven Knoth
F. F. Gan (1991), EWMA control chart under linear drift, J. Stat. Comput. Simulation 38, 181-200.
L. A. Aerne, C. W. Champ and S. E. Rigdon (1991), Evaluation of control charts under linear trend, Commun. Stat., Theory Methods 20, 3341-3349.
xshewhartrunsrules.arl
for zero-state ARL computation of
Shewhart control charts with and without runs rules
for the classical step change model.
## Aerne et al. (1991) ## Table I (continued) ## original numbers are # delta arl1of1 arl2of3 arl4of5 arl10 # 0.005623 136.67 120.90 105.34 107.08 # 0.007499 114.98 101.23 88.09 89.94 # 0.010000 96.03 84.22 73.31 75.23 # 0.013335 79.69 69.68 60.75 62.73 # 0.017783 65.75 57.38 50.18 52.18 # 0.023714 53.99 47.06 41.33 43.35 # 0.031623 44.15 38.47 33.99 36.00 # 0.042170 35.97 31.36 27.91 29.90 # 0.056234 29.21 25.51 22.91 24.86 # 0.074989 23.65 20.71 18.81 20.70 # 0.100000 19.11 16.79 15.45 17.29 # 0.133352 15.41 13.61 12.72 14.47 # 0.177828 12.41 11.03 10.50 12.14 # 0.237137 9.98 8.94 8.71 10.18 # 0.316228 8.02 7.25 7.26 8.45 # 0.421697 6.44 5.89 6.09 6.84 # 0.562341 5.17 4.80 5.15 5.48 # 0.749894 4.16 3.92 4.36 4.39 # 1.000000 3.35 3.22 3.63 3.52 c1of1 <- 3.069/3 c2of3 <- 2.1494/2 c4of5 <- 1.14 c10 <- 3.2425/3 DxDshewhartrunsrules.arl <- Vectorize(xDshewhartrunsrules.arl, "delta") deltas <- 10^(-(18:0)/8) arl1of1 <- round(DxDshewhartrunsrules.arl(deltas, c=c1of1, type="1"), digits=2) arl2of3 <- round(DxDshewhartrunsrules.arl(deltas, c=c2of3, type="12"), digits=2) arl4of5 <- round(DxDshewhartrunsrules.arl(deltas, c=c4of5, type="13"), digits=2) arl10 <- round(DxDshewhartrunsrules.arl(deltas, c=c10, type="SameSide10"), digits=2) data.frame(delta=round(deltas, digits=6), arl1of1, arl2of3, arl4of5, arl10)
## Aerne et al. (1991) ## Table I (continued) ## original numbers are # delta arl1of1 arl2of3 arl4of5 arl10 # 0.005623 136.67 120.90 105.34 107.08 # 0.007499 114.98 101.23 88.09 89.94 # 0.010000 96.03 84.22 73.31 75.23 # 0.013335 79.69 69.68 60.75 62.73 # 0.017783 65.75 57.38 50.18 52.18 # 0.023714 53.99 47.06 41.33 43.35 # 0.031623 44.15 38.47 33.99 36.00 # 0.042170 35.97 31.36 27.91 29.90 # 0.056234 29.21 25.51 22.91 24.86 # 0.074989 23.65 20.71 18.81 20.70 # 0.100000 19.11 16.79 15.45 17.29 # 0.133352 15.41 13.61 12.72 14.47 # 0.177828 12.41 11.03 10.50 12.14 # 0.237137 9.98 8.94 8.71 10.18 # 0.316228 8.02 7.25 7.26 8.45 # 0.421697 6.44 5.89 6.09 6.84 # 0.562341 5.17 4.80 5.15 5.48 # 0.749894 4.16 3.92 4.36 4.39 # 1.000000 3.35 3.22 3.63 3.52 c1of1 <- 3.069/3 c2of3 <- 2.1494/2 c4of5 <- 1.14 c10 <- 3.2425/3 DxDshewhartrunsrules.arl <- Vectorize(xDshewhartrunsrules.arl, "delta") deltas <- 10^(-(18:0)/8) arl1of1 <- round(DxDshewhartrunsrules.arl(deltas, c=c1of1, type="1"), digits=2) arl2of3 <- round(DxDshewhartrunsrules.arl(deltas, c=c2of3, type="12"), digits=2) arl4of5 <- round(DxDshewhartrunsrules.arl(deltas, c=c4of5, type="13"), digits=2) arl10 <- round(DxDshewhartrunsrules.arl(deltas, c=c10, type="SameSide10"), digits=2) data.frame(delta=round(deltas, digits=6), arl1of1, arl2of3, arl4of5, arl10)
Computation of the steady-state Average Run Length (ARL) for different types of EWMA control charts monitoring normal mean.
xewma.ad(l, c, mu1, mu0=0, zr=0, z0=0, sided="one", limits="fix", steady.state.mode="conditional", r=40)
xewma.ad(l, c, mu1, mu0=0, zr=0, z0=0, sided="one", limits="fix", steady.state.mode="conditional", r=40)
l |
smoothing parameter lambda of the EWMA control chart. |
c |
critical value (similar to alarm limit) of the EWMA control chart. |
mu1 |
out-of-control mean. |
mu0 |
in-control mean. |
zr |
reflection border for the one-sided chart. |
z0 |
restarting value of the EWMA sequence in case of a false alarm in
|
sided |
distinguishes between one- and two-sided two-sided EWMA control
chart by choosing |
limits |
distinguishes between different control limits behavior. |
steady.state.mode |
distinguishes between two steady-state modes – conditional and cyclical. |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
xewma.ad
determines the steady-state Average Run Length (ARL)
by numerically solving the related ARL integral equation by means
of the Nystroem method based on Gauss-Legendre quadrature
and using the power method for deriving the largest in magnitude
eigenvalue and the related left eigenfunction.
Returns a single value which resembles the steady-state ARL.
Sven Knoth
R. B. Crosier (1986), A new two-sided cumulative quality control scheme, Technometrics 28, 187-194.
S. V. Crowder (1987), A simple method for studying run-length distributions of exponentially weighted moving average charts, Technometrics 29, 401-407.
J. M. Lucas and M. S. Saccucci (1990), Exponentially weighted moving average control schemes: Properties and enhancements, Technometrics 32, 1-12.
xewma.arl
for zero-state ARL computation and
xcusum.ad
for the steady-state ARL of CUSUM control charts.
## comparison of zero-state (= worst case ) and steady-state performance ## for two-sided EWMA control charts l <- .1 c <- xewma.crit(l,500,sided="two") mu <- c(0,.5,1,1.5,2) arl <- sapply(mu,l=l,c=c,sided="two",xewma.arl) ad <- sapply(mu,l=l,c=c,sided="two",xewma.ad) round(cbind(mu,arl,ad),digits=2) ## Lucas/Saccucci (1990) ## two-sided EWMA ## with fixed limits l1 <- .5 l2 <- .03 c1 <- 3.071 c2 <- 2.437 mu <- c(0,.25,.5,.75,1,1.5,2,2.5,3,3.5,4,5) ad1 <- sapply(mu,l=l1,c=c1,sided="two",xewma.ad) ad2 <- sapply(mu,l=l2,c=c2,sided="two",xewma.ad) round(cbind(mu,ad1,ad2),digits=2) ## original results are (in Table 3) ## 0.00 499. 480. ## 0.25 254. 74.1 ## 0.50 88.4 28.6 ## 0.75 35.7 17.3 ## 1.00 17.3 12.5 ## 1.50 6.44 8.00 ## 2.00 3.58 5.95 ## 2.50 2.47 4.78 ## 3.00 1.91 4.02 ## 3.50 1.58 3.49 ## 4.00 1.36 3.09 ## 5.00 1.10 2.55
## comparison of zero-state (= worst case ) and steady-state performance ## for two-sided EWMA control charts l <- .1 c <- xewma.crit(l,500,sided="two") mu <- c(0,.5,1,1.5,2) arl <- sapply(mu,l=l,c=c,sided="two",xewma.arl) ad <- sapply(mu,l=l,c=c,sided="two",xewma.ad) round(cbind(mu,arl,ad),digits=2) ## Lucas/Saccucci (1990) ## two-sided EWMA ## with fixed limits l1 <- .5 l2 <- .03 c1 <- 3.071 c2 <- 2.437 mu <- c(0,.25,.5,.75,1,1.5,2,2.5,3,3.5,4,5) ad1 <- sapply(mu,l=l1,c=c1,sided="two",xewma.ad) ad2 <- sapply(mu,l=l2,c=c2,sided="two",xewma.ad) round(cbind(mu,ad1,ad2),digits=2) ## original results are (in Table 3) ## 0.00 499. 480. ## 0.25 254. 74.1 ## 0.50 88.4 28.6 ## 0.75 35.7 17.3 ## 1.00 17.3 12.5 ## 1.50 6.44 8.00 ## 2.00 3.58 5.95 ## 2.50 2.47 4.78 ## 3.00 1.91 4.02 ## 3.50 1.58 3.49 ## 4.00 1.36 3.09 ## 5.00 1.10 2.55
Computation of the (zero-state) Average Run Length (ARL) for different types of EWMA control charts monitoring normal mean.
xewma.arl(l,cE,mu,zr=0,hs=0,sided="one",limits="fix",q=1, steady.state.mode="conditional",r=40)
xewma.arl(l,cE,mu,zr=0,hs=0,sided="one",limits="fix",q=1, steady.state.mode="conditional",r=40)
l |
smoothing parameter lambda of the EWMA control chart. |
cE |
critical value (similar to alarm limit) of the EWMA control chart. |
mu |
true mean. |
zr |
reflection border for the one-sided chart. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided EWMA control chart
by choosing |
limits |
distinguishes between different control limits behavior. |
q |
change point position. For |
steady.state.mode |
distinguishes between two steady-state modes – conditional and cyclical
(needed for |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
In case of the EWMA chart with fixed control limits,
xewma.arl
determines the Average Run Length (ARL) by numerically
solving the related ARL integral equation by means of the Nystroem method
based on Gauss-Legendre quadrature.
If limits
is not "fix"
, then the method presented in Knoth (2003) is utilized.
Note that for one-sided EWMA charts (sided
="one"
), only
"vacl"
and "stat"
are deployed, while for two-sided ones
(sided
="two"
) also "fir"
, "both"
(combination of "fir"
and "vacl"
), "Steiner"
and "cfar"
are implemented.
For details see Knoth (2004).
Except for the fixed limits EWMA charts it returns a single value which resembles the ARL.
For fixed limits charts, it returns a vector of length q
which resembles the ARL and the
sequence of conditional expected delays for
q
=1 and q
>1, respectively.
Sven Knoth
K.-H. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, Appl. Statist. 35, 151-158.
S. V. Crowder (1987), A simple method for studying run-length distributions of exponentially weighted moving average charts, Technometrics 29, 401-407.
J. M. Lucas and M. S. Saccucci (1990), Exponentially weighted moving average control schemes: Properties and enhancements, Technometrics 32, 1-12.
S. Chandrasekaran, J. R. English and R. L. Disney (1995), Modeling and analysis of EWMA control schemes with variance-adjusted control limits, IIE Transactions 277, 282-290.
T. R. Rhoads, D. C. Montgomery and C. M. Mastrangelo (1996), Fast initial response scheme for exponentially weighted moving average control chart, Quality Engineering 9, 317-327.
S. H. Steiner (1999), EWMA control charts with time-varying control limits and fast initial response, Journal of Quality Technology 31, 75-86.
S. Knoth (2003), EWMA schemes with non-homogeneous transition kernels, Sequential Analysis 22, 241-255.
S. Knoth (2004), Fast initial response features for EWMA Control Charts, Statistical Papers 46, 47-64.
xcusum.arl
for zero-state ARL computation of CUSUM control charts
and xewma.ad
for the steady-state ARL.
## Waldmann (1986), one-sided EWMA l <- .75 round(xewma.arl(l,2*sqrt((2-l)/l),0,zr=-4*sqrt((2-l)/l)),digits=1) l <- .5 round(xewma.arl(l,2*sqrt((2-l)/l),0,zr=-4*sqrt((2-l)/l)),digits=1) ## original values are 209.3 and 3907.5 (in Table 2). ## Waldmann (1986), two-sided EWMA with fixed control limits l <- .75 round(xewma.arl(l,2*sqrt((2-l)/l),0,sided="two"),digits=1) l <- .5 round(xewma.arl(l,2*sqrt((2-l)/l),0,sided="two"),digits=1) ## original values are 104.0 and 1952 (in Table 1). ## Crowder (1987), two-sided EWMA with fixed control limits l1 <- .5 l2 <- .05 cE <- 2 mu <- (0:16)/4 arl1 <- sapply(mu,l=l1,cE=cE,sided="two",xewma.arl) arl2 <- sapply(mu,l=l2,cE=cE,sided="two",xewma.arl) round(cbind(mu,arl1,arl2),digits=2) ## original results are (in Table 1) ## 0.00 26.45 127.53 ## 0.25 20.12 43.94 ## 0.50 11.89 18.97 ## 0.75 7.29 11.64 ## 1.00 4.91 8.38 ## 1.25 3.95* 6.56 ## 1.50 2.80 5.41 ## 1.75 2.29 4.62 ## 2.00 1.94 4.04 ## 2.25 1.70 3.61 ## 2.50 1.51 3.26 ## 2.75 1.37 2.99 ## 3.00 1.26 2.76 ## 3.25 1.18 2.56 ## 3.50 1.12 2.39 ## 3.75 1.08 2.26 ## 4.00 1.05 2.15 (* -- in Crowder (1987) typo!?) ## Lucas/Saccucci (1990) ## two-sided EWMA ## with fixed limits l1 <- .5 l2 <- .03 c1 <- 3.071 c2 <- 2.437 mu <- c(0,.25,.5,.75,1,1.5,2,2.5,3,3.5,4,5) arl1 <- sapply(mu,l=l1,cE=c1,sided="two",xewma.arl) arl2 <- sapply(mu,l=l2,cE=c2,sided="two",xewma.arl) round(cbind(mu,arl1,arl2),digits=2) ## original results are (in Table 3) ## 0.00 500. 500. ## 0.25 255. 76.7 ## 0.50 88.8 29.3 ## 0.75 35.9 17.6 ## 1.00 17.5 12.6 ## 1.50 6.53 8.07 ## 2.00 3.63 5.99 ## 2.50 2.50 4.80 ## 3.00 1.93 4.03 ## 3.50 1.58 3.49 ## 4.00 1.34 3.11 ## 5.00 1.07 2.55 ## Not run: ## with fir feature l1 <- .5 l2 <- .03 c1 <- 3.071 c2 <- 2.437 hs1 <- c1/2 hs2 <- c2/2 mu <- c(0,.5,1,2,3,5) arl1 <- sapply(mu,l=l1,cE=c1,hs=hs1,sided="two",limits="fir",xewma.arl) arl2 <- sapply(mu,l=l2,cE=c2,hs=hs2,sided="two",limits="fir",xewma.arl) round(cbind(mu,arl1,arl2),digits=2) ## original results are (in Table 5) ## 0.0 487. 406. ## 0.5 86.1 18.4 ## 1.0 15.9 7.36 ## 2.0 2.87 3.43 ## 3.0 1.45 2.34 ## 5.0 1.01 1.57 ## Chandrasekaran, English, Disney (1995) ## two-sided EWMA with fixed and variance adjusted limits (vacl) l1 <- .25 l2 <- .1 c1s <- 2.9985 c1n <- 3.0042 c2s <- 2.8159 c2n <- 2.8452 mu <- c(0,.25,.5,.75,1,2) arl1s <- sapply(mu,l=l1,cE=c1s,sided="two",xewma.arl) arl1n <- sapply(mu,l=l1,cE=c1n,sided="two",limits="vacl",xewma.arl) arl2s <- sapply(mu,l=l2,cE=c2s,sided="two",xewma.arl) arl2n <- sapply(mu,l=l2,cE=c2n,sided="two",limits="vacl",xewma.arl) round(cbind(mu,arl1s,arl1n,arl2s,arl2n),digits=2) ## original results are (in Table 2) ## 0.00 500. 500. 500. 500. ## 0.25 170.09 167.54 105.90 96.6 ## 0.50 48.14 45.65 31.08 24.35 ## 0.75 20.02 19.72 15.71 10.74 ## 1.00 11.07 9.37 10.23 6.35 ## 2.00 3.59 2.64 4.32 2.73 ## The results in Chandrasekaran, English, Disney (1995) are not ## that accurate. Let us consider the more appropriate comparison c1s <- xewma.crit(l1,500,sided="two") c1n <- xewma.crit(l1,500,sided="two",limits="vacl") c2s <- xewma.crit(l2,500,sided="two") c2n <- xewma.crit(l2,500,sided="two",limits="vacl") mu <- c(0,.25,.5,.75,1,2) arl1s <- sapply(mu,l=l1,cE=c1s,sided="two",xewma.arl) arl1n <- sapply(mu,l=l1,cE=c1n,sided="two",limits="vacl",xewma.arl) arl2s <- sapply(mu,l=l2,cE=c2s,sided="two",xewma.arl) arl2n <- sapply(mu,l=l2,cE=c2n,sided="two",limits="vacl",xewma.arl) round(cbind(mu,arl1s,arl1n,arl2s,arl2n),digits=2) ## which demonstrate the abilities of the variance-adjusted limits ## scheme more explicitely. ## Rhoads, Montgomery, Mastrangelo (1996) ## two-sided EWMA with fixed and variance adjusted limits (vacl), ## with fir and both features l <- .03 cE <- 2.437 mu <- c(0,.5,1,1.5,2,3,4) sl <- sqrt(l*(2-l)) arlfix <- sapply(mu,l=l,cE=cE,sided="two",xewma.arl) arlvacl <- sapply(mu,l=l,cE=cE,sided="two",limits="vacl",xewma.arl) arlfir <- sapply(mu,l=l,cE=cE,hs=c/2,sided="two",limits="fir",xewma.arl) arlboth <- sapply(mu,l=l,cE=cE,hs=c/2*sl,sided="two",limits="both",xewma.arl) round(cbind(mu,arlfix,arlvacl,arlfir,arlboth),digits=1) ## original results are (in Table 1) ## 0.0 477.3* 427.9* 383.4* 286.2* ## 0.5 29.7 20.0 18.6 12.8 ## 1.0 12.5 6.5 7.4 3.6 ## 1.5 8.1 3.3 4.6 1.9 ## 2.0 6.0 2.2 3.4 1.4 ## 3.0 4.0 1.3 2.4 1.0 ## 4.0 3.1 1.1 1.9 1.0 ## * -- the in-control values differ sustainably from the true values! ## Steiner (1999) ## two-sided EWMA control charts with various modifications ## fixed vs. variance adjusted limits l <- .05 cE <- 3 mu <- c(0,.25,.5,.75,1,1.5,2,2.5,3,3.5,4) arlfix <- sapply(mu,l=l,cE=cE,sided="two",xewma.arl) arlvacl <- sapply(mu,l=l,cE=cE,sided="two",limits="vacl",xewma.arl) round(cbind(mu,arlfix,arlvacl),digits=1) ## original results are (in Table 2) ## 0.00 1379.0 1353.0 ## 0.25 135.0 127.0 ## 0.50 37.4 32.5 ## 0.75 20.0 15.6 ## 1.00 13.5 9.0 ## 1.50 8.3 4.5 ## 2.00 6.0 2.8 ## 2.50 4.8 2.0 ## 3.00 4.0 1.6 ## 3.50 3.4 1.3 ## 4.00 3.0 1.1 ## fir, both, and Steiner's modification l <- .03 cfir <- 2.44 cboth <- 2.54 cstein <- 2.55 hsfir <- cfir/2 hsboth <- cboth/2*sqrt(l*(2-l)) mu <- c(0,.5,1,1.5,2,3,4) arlfir <- sapply(mu,l=l,cE=cfir,hs=hsfir,sided="two",limits="fir",xewma.arl) arlboth <- sapply(mu,l=l,cE=cboth,hs=hsboth,sided="two",limits="both",xewma.arl) arlstein <- sapply(mu,l=l,cE=cstein,sided="two",limits="Steiner",xewma.arl) round(cbind(mu,arlfir,arlboth,arlstein),digits=1) ## original values are (in Table 5) ## 0.0 383.0 384.0 391.0 ## 0.5 18.6 14.9 13.8 ## 1.0 7.4 3.9 3.6 ## 1.5 4.6 2.0 1.8 ## 2.0 3.4 1.4 1.3 ## 3.0 2.4 1.1 1.0 ## 4.0 1.9 1.0 1.0 ## SAS/QC manual 1999 ## two-sided EWMA control charts with fixed limits l <- .25 cE <- 3 mu <- 1 print(xewma.arl(l,cE,mu,sided="two"),digits=11) # original value is 11.154267016. ## Some recent examples for one-sided EWMA charts ## with varying limits and in the so-called stationary mode # 1. varying limits = "vacl" lambda <- .1 L0 <- 500 ## Monte Carlo results (10^9 replicates) # mu ARL s.e. # 0 500.00 0.0160 # 0.5 21.637 0.0006 # 1 6.7596 0.0001 # 1.5 3.5398 0.0001 # 2 2.3038 0.0000 # 2.5 1.7004 0.0000 # 3 1.3675 0.0000 zr <- -6 r <- 50 cE <- xewma.crit(lambda, L0, zr=zr, limits="vacl", r=r) Mxewma.arl <- Vectorize(xewma.arl, "mu") mus <- (0:6)/2 arls <- round(Mxewma.arl(lambda, cE, mus, zr=zr, limits="vacl", r=r), digits=4) data.frame(mus, arls) # 2. stationary mode, i. e. limits = "stat" ## Monte Carlo results (10^9 replicates) # mu ARL s.e. # 0 500.00 0.0159 # 0.5 22.313 0.0006 # 1 7.2920 0.0001 # 1.5 3.9064 0.0001 # 2 2.5131 0.0000 # 2.5 1.7983 0.0000 # 3 1.4029 0.0000 cE <- xewma.crit(lambda, L0, zr=zr, limits="stat", r=r) arls <- round(Mxewma.arl(lambda, cE, mus, zr=zr, limits="stat", r=r), digits=4) data.frame(mus, arls) ## End(Not run)
## Waldmann (1986), one-sided EWMA l <- .75 round(xewma.arl(l,2*sqrt((2-l)/l),0,zr=-4*sqrt((2-l)/l)),digits=1) l <- .5 round(xewma.arl(l,2*sqrt((2-l)/l),0,zr=-4*sqrt((2-l)/l)),digits=1) ## original values are 209.3 and 3907.5 (in Table 2). ## Waldmann (1986), two-sided EWMA with fixed control limits l <- .75 round(xewma.arl(l,2*sqrt((2-l)/l),0,sided="two"),digits=1) l <- .5 round(xewma.arl(l,2*sqrt((2-l)/l),0,sided="two"),digits=1) ## original values are 104.0 and 1952 (in Table 1). ## Crowder (1987), two-sided EWMA with fixed control limits l1 <- .5 l2 <- .05 cE <- 2 mu <- (0:16)/4 arl1 <- sapply(mu,l=l1,cE=cE,sided="two",xewma.arl) arl2 <- sapply(mu,l=l2,cE=cE,sided="two",xewma.arl) round(cbind(mu,arl1,arl2),digits=2) ## original results are (in Table 1) ## 0.00 26.45 127.53 ## 0.25 20.12 43.94 ## 0.50 11.89 18.97 ## 0.75 7.29 11.64 ## 1.00 4.91 8.38 ## 1.25 3.95* 6.56 ## 1.50 2.80 5.41 ## 1.75 2.29 4.62 ## 2.00 1.94 4.04 ## 2.25 1.70 3.61 ## 2.50 1.51 3.26 ## 2.75 1.37 2.99 ## 3.00 1.26 2.76 ## 3.25 1.18 2.56 ## 3.50 1.12 2.39 ## 3.75 1.08 2.26 ## 4.00 1.05 2.15 (* -- in Crowder (1987) typo!?) ## Lucas/Saccucci (1990) ## two-sided EWMA ## with fixed limits l1 <- .5 l2 <- .03 c1 <- 3.071 c2 <- 2.437 mu <- c(0,.25,.5,.75,1,1.5,2,2.5,3,3.5,4,5) arl1 <- sapply(mu,l=l1,cE=c1,sided="two",xewma.arl) arl2 <- sapply(mu,l=l2,cE=c2,sided="two",xewma.arl) round(cbind(mu,arl1,arl2),digits=2) ## original results are (in Table 3) ## 0.00 500. 500. ## 0.25 255. 76.7 ## 0.50 88.8 29.3 ## 0.75 35.9 17.6 ## 1.00 17.5 12.6 ## 1.50 6.53 8.07 ## 2.00 3.63 5.99 ## 2.50 2.50 4.80 ## 3.00 1.93 4.03 ## 3.50 1.58 3.49 ## 4.00 1.34 3.11 ## 5.00 1.07 2.55 ## Not run: ## with fir feature l1 <- .5 l2 <- .03 c1 <- 3.071 c2 <- 2.437 hs1 <- c1/2 hs2 <- c2/2 mu <- c(0,.5,1,2,3,5) arl1 <- sapply(mu,l=l1,cE=c1,hs=hs1,sided="two",limits="fir",xewma.arl) arl2 <- sapply(mu,l=l2,cE=c2,hs=hs2,sided="two",limits="fir",xewma.arl) round(cbind(mu,arl1,arl2),digits=2) ## original results are (in Table 5) ## 0.0 487. 406. ## 0.5 86.1 18.4 ## 1.0 15.9 7.36 ## 2.0 2.87 3.43 ## 3.0 1.45 2.34 ## 5.0 1.01 1.57 ## Chandrasekaran, English, Disney (1995) ## two-sided EWMA with fixed and variance adjusted limits (vacl) l1 <- .25 l2 <- .1 c1s <- 2.9985 c1n <- 3.0042 c2s <- 2.8159 c2n <- 2.8452 mu <- c(0,.25,.5,.75,1,2) arl1s <- sapply(mu,l=l1,cE=c1s,sided="two",xewma.arl) arl1n <- sapply(mu,l=l1,cE=c1n,sided="two",limits="vacl",xewma.arl) arl2s <- sapply(mu,l=l2,cE=c2s,sided="two",xewma.arl) arl2n <- sapply(mu,l=l2,cE=c2n,sided="two",limits="vacl",xewma.arl) round(cbind(mu,arl1s,arl1n,arl2s,arl2n),digits=2) ## original results are (in Table 2) ## 0.00 500. 500. 500. 500. ## 0.25 170.09 167.54 105.90 96.6 ## 0.50 48.14 45.65 31.08 24.35 ## 0.75 20.02 19.72 15.71 10.74 ## 1.00 11.07 9.37 10.23 6.35 ## 2.00 3.59 2.64 4.32 2.73 ## The results in Chandrasekaran, English, Disney (1995) are not ## that accurate. Let us consider the more appropriate comparison c1s <- xewma.crit(l1,500,sided="two") c1n <- xewma.crit(l1,500,sided="two",limits="vacl") c2s <- xewma.crit(l2,500,sided="two") c2n <- xewma.crit(l2,500,sided="two",limits="vacl") mu <- c(0,.25,.5,.75,1,2) arl1s <- sapply(mu,l=l1,cE=c1s,sided="two",xewma.arl) arl1n <- sapply(mu,l=l1,cE=c1n,sided="two",limits="vacl",xewma.arl) arl2s <- sapply(mu,l=l2,cE=c2s,sided="two",xewma.arl) arl2n <- sapply(mu,l=l2,cE=c2n,sided="two",limits="vacl",xewma.arl) round(cbind(mu,arl1s,arl1n,arl2s,arl2n),digits=2) ## which demonstrate the abilities of the variance-adjusted limits ## scheme more explicitely. ## Rhoads, Montgomery, Mastrangelo (1996) ## two-sided EWMA with fixed and variance adjusted limits (vacl), ## with fir and both features l <- .03 cE <- 2.437 mu <- c(0,.5,1,1.5,2,3,4) sl <- sqrt(l*(2-l)) arlfix <- sapply(mu,l=l,cE=cE,sided="two",xewma.arl) arlvacl <- sapply(mu,l=l,cE=cE,sided="two",limits="vacl",xewma.arl) arlfir <- sapply(mu,l=l,cE=cE,hs=c/2,sided="two",limits="fir",xewma.arl) arlboth <- sapply(mu,l=l,cE=cE,hs=c/2*sl,sided="two",limits="both",xewma.arl) round(cbind(mu,arlfix,arlvacl,arlfir,arlboth),digits=1) ## original results are (in Table 1) ## 0.0 477.3* 427.9* 383.4* 286.2* ## 0.5 29.7 20.0 18.6 12.8 ## 1.0 12.5 6.5 7.4 3.6 ## 1.5 8.1 3.3 4.6 1.9 ## 2.0 6.0 2.2 3.4 1.4 ## 3.0 4.0 1.3 2.4 1.0 ## 4.0 3.1 1.1 1.9 1.0 ## * -- the in-control values differ sustainably from the true values! ## Steiner (1999) ## two-sided EWMA control charts with various modifications ## fixed vs. variance adjusted limits l <- .05 cE <- 3 mu <- c(0,.25,.5,.75,1,1.5,2,2.5,3,3.5,4) arlfix <- sapply(mu,l=l,cE=cE,sided="two",xewma.arl) arlvacl <- sapply(mu,l=l,cE=cE,sided="two",limits="vacl",xewma.arl) round(cbind(mu,arlfix,arlvacl),digits=1) ## original results are (in Table 2) ## 0.00 1379.0 1353.0 ## 0.25 135.0 127.0 ## 0.50 37.4 32.5 ## 0.75 20.0 15.6 ## 1.00 13.5 9.0 ## 1.50 8.3 4.5 ## 2.00 6.0 2.8 ## 2.50 4.8 2.0 ## 3.00 4.0 1.6 ## 3.50 3.4 1.3 ## 4.00 3.0 1.1 ## fir, both, and Steiner's modification l <- .03 cfir <- 2.44 cboth <- 2.54 cstein <- 2.55 hsfir <- cfir/2 hsboth <- cboth/2*sqrt(l*(2-l)) mu <- c(0,.5,1,1.5,2,3,4) arlfir <- sapply(mu,l=l,cE=cfir,hs=hsfir,sided="two",limits="fir",xewma.arl) arlboth <- sapply(mu,l=l,cE=cboth,hs=hsboth,sided="two",limits="both",xewma.arl) arlstein <- sapply(mu,l=l,cE=cstein,sided="two",limits="Steiner",xewma.arl) round(cbind(mu,arlfir,arlboth,arlstein),digits=1) ## original values are (in Table 5) ## 0.0 383.0 384.0 391.0 ## 0.5 18.6 14.9 13.8 ## 1.0 7.4 3.9 3.6 ## 1.5 4.6 2.0 1.8 ## 2.0 3.4 1.4 1.3 ## 3.0 2.4 1.1 1.0 ## 4.0 1.9 1.0 1.0 ## SAS/QC manual 1999 ## two-sided EWMA control charts with fixed limits l <- .25 cE <- 3 mu <- 1 print(xewma.arl(l,cE,mu,sided="two"),digits=11) # original value is 11.154267016. ## Some recent examples for one-sided EWMA charts ## with varying limits and in the so-called stationary mode # 1. varying limits = "vacl" lambda <- .1 L0 <- 500 ## Monte Carlo results (10^9 replicates) # mu ARL s.e. # 0 500.00 0.0160 # 0.5 21.637 0.0006 # 1 6.7596 0.0001 # 1.5 3.5398 0.0001 # 2 2.3038 0.0000 # 2.5 1.7004 0.0000 # 3 1.3675 0.0000 zr <- -6 r <- 50 cE <- xewma.crit(lambda, L0, zr=zr, limits="vacl", r=r) Mxewma.arl <- Vectorize(xewma.arl, "mu") mus <- (0:6)/2 arls <- round(Mxewma.arl(lambda, cE, mus, zr=zr, limits="vacl", r=r), digits=4) data.frame(mus, arls) # 2. stationary mode, i. e. limits = "stat" ## Monte Carlo results (10^9 replicates) # mu ARL s.e. # 0 500.00 0.0159 # 0.5 22.313 0.0006 # 1 7.2920 0.0001 # 1.5 3.9064 0.0001 # 2 2.5131 0.0000 # 2.5 1.7983 0.0000 # 3 1.4029 0.0000 cE <- xewma.crit(lambda, L0, zr=zr, limits="stat", r=r) arls <- round(Mxewma.arl(lambda, cE, mus, zr=zr, limits="stat", r=r), digits=4) data.frame(mus, arls) ## End(Not run)
Computation of the (zero-state) Average Run Length (ARL) function for different types of EWMA control charts monitoring normal mean.
xewma.arl.f(l,c,mu,zr=0,sided="one",limits="fix",r=40)
xewma.arl.f(l,c,mu,zr=0,sided="one",limits="fix",r=40)
l |
smoothing parameter lambda of the EWMA control chart. |
c |
critical value (similar to alarm limit) of the EWMA control chart. |
mu |
true mean. |
zr |
reflection border for the one-sided chart. |
sided |
distinguishes between one- and two-sided EWMA control chart by choosing |
limits |
distinguishes between different control limits behavior. |
r |
number of quadrature nodes, dimension of the resulting linear equation system is equal to |
It is a convenience function to yield the ARL as function of the head start hs
. For more details see xewma.arl
.
It returns a function of a single argument, hs=x
which maps the head-start value hs
to the ARL.
Sven Knoth
S. V. Crowder (1987), A simple method for studying run-length distributions of exponentially weighted moving average charts, Technometrics 29, 401-407.
xewma.arl
for zero-state ARL for one specific head-start hs
.
# will follow
# will follow
Computation of the (zero-state) Average Run Length (ARL) for different types of EWMA control charts monitoring normal mean if the in-control mean, standard deviation, or both are estimated by a pre run.
xewma.arl.prerun(l, c, mu, zr=0, hs=0, sided="two", limits="fix", q=1, size=100, df=NULL, estimated="mu", qm.mu=30, qm.sigma=30, truncate=1e-10) xewma.crit.prerun(l, L0, mu, zr=0, hs=0, sided="two", limits="fix", size=100, df=NULL, estimated="mu", qm.mu=30, qm.sigma=30, truncate=1e-10, c.error=1e-12, L.error=1e-9, OUTPUT=FALSE)
xewma.arl.prerun(l, c, mu, zr=0, hs=0, sided="two", limits="fix", q=1, size=100, df=NULL, estimated="mu", qm.mu=30, qm.sigma=30, truncate=1e-10) xewma.crit.prerun(l, L0, mu, zr=0, hs=0, sided="two", limits="fix", size=100, df=NULL, estimated="mu", qm.mu=30, qm.sigma=30, truncate=1e-10, c.error=1e-12, L.error=1e-9, OUTPUT=FALSE)
l |
smoothing parameter lambda of the EWMA control chart. |
c |
critical value (similar to alarm limit) of the EWMA control chart. |
mu |
true mean shift. |
zr |
reflection border for the one-sided chart. |
hs |
so-called headstart (give fast initial response). |
sided |
distinguish between one- and two-sided EWMA control chart
by choosing |
limits |
distinguish between different control limits behavior. |
q |
change point position. For |
size |
pre run sample size. |
df |
Degrees of freedom of the pre run variance estimator. Typically it is simply |
estimated |
name the parameter to be estimated within
the |
qm.mu |
number of quadrature nodes for convoluting the mean uncertainty. |
qm.sigma |
number of quadrature nodes for convoluting the standard deviation uncertainty. |
truncate |
size of truncated tail. |
L0 |
in-control ARL. |
c.error |
error bound for two succeeding values of the critical value during applying the secant rule. |
L.error |
error bound for the ARL level |
OUTPUT |
activate or deactivate additional output. |
Essentially, the ARL function xewma.arl
is convoluted with the
distribution of the sample mean, standard deviation or both.
For details see Jones/Champ/Rigdon (2001) and Knoth (2014?).
Returns a single value which resembles the ARL.
Sven Knoth
L. A. Jones, C. W. Champ, S. E. Rigdon (2001), The performance of exponentially weighted moving average charts with estimated parameters, Technometrics 43, 156-167.
S. Knoth (2003), EWMA schemes with non-homogeneous transition kernels, Sequential Analysis 22, 241-255.
S. Knoth (2004), Fast initial response features for EWMA Control Charts, Statistical Papers 46, 47-64.
S. Knoth (2014?), tbd, tbd, tbd-tbd.
xewma.arl
for the usual zero-state ARL computation.
## Jones/Champ/Rigdon (2001) c4m <- function(m, n) sqrt(2)*gamma( (m*(n-1)+1)/2 )/sqrt( m*(n-1) )/gamma( m*(n-1)/2 ) n <- 5 # sample size m <- 20 # pre run with 20 samples of size n = 5 C4m <- c4m(m, n) # needed for bias correction # Table 1, 3rd column lambda <- 0.2 L <- 2.636 xewma.ARL <- Vectorize("xewma.arl", "mu") xewma.ARL.prerun <- Vectorize("xewma.arl.prerun", "mu") mu <- c(0, .25, .5, 1, 1.5, 2) ARL <- round(xewma.ARL(lambda, L, mu, sided="two"), digits=2) p.ARL <- round(xewma.ARL.prerun(lambda, L/C4m, mu, sided="two", size=m, df=m*(n-1), estimated="both", qm.mu=70), digits=2) # Monte-Carlo with 10^8 repetitions: 200.325 (0.020) and 144.458 (0.022) cbind(mu, ARL, p.ARL) ## Not run: # Figure 5, subfigure r = 0.2 mu_ <- (0:85)/40 ARL_ <- round(xewma.ARL(lambda, L, mu_, sided="two"), digits=2) p.ARL_ <- round(xewma.ARL.prerun(lambda, L/C4m, mu_, sided="two", size=m, df=m*(n-1), estimated="both"), digits=2) plot(mu_, ARL_, type="l", xlab=expression(delta), ylab="ARL", xlim=c(0,2)) abline(v=0, h=0, col="grey", lwd=.7) points(mu, ARL, pch=5) lines(mu_, p.ARL_, col="blue") points(mu, p.ARL, pch=18, col ="blue") legend("topright", c("Known", "Estimated"), col=c("black", "blue"), lty=1, pch=c(5, 18)) ## End(Not run)
## Jones/Champ/Rigdon (2001) c4m <- function(m, n) sqrt(2)*gamma( (m*(n-1)+1)/2 )/sqrt( m*(n-1) )/gamma( m*(n-1)/2 ) n <- 5 # sample size m <- 20 # pre run with 20 samples of size n = 5 C4m <- c4m(m, n) # needed for bias correction # Table 1, 3rd column lambda <- 0.2 L <- 2.636 xewma.ARL <- Vectorize("xewma.arl", "mu") xewma.ARL.prerun <- Vectorize("xewma.arl.prerun", "mu") mu <- c(0, .25, .5, 1, 1.5, 2) ARL <- round(xewma.ARL(lambda, L, mu, sided="two"), digits=2) p.ARL <- round(xewma.ARL.prerun(lambda, L/C4m, mu, sided="two", size=m, df=m*(n-1), estimated="both", qm.mu=70), digits=2) # Monte-Carlo with 10^8 repetitions: 200.325 (0.020) and 144.458 (0.022) cbind(mu, ARL, p.ARL) ## Not run: # Figure 5, subfigure r = 0.2 mu_ <- (0:85)/40 ARL_ <- round(xewma.ARL(lambda, L, mu_, sided="two"), digits=2) p.ARL_ <- round(xewma.ARL.prerun(lambda, L/C4m, mu_, sided="two", size=m, df=m*(n-1), estimated="both"), digits=2) plot(mu_, ARL_, type="l", xlab=expression(delta), ylab="ARL", xlim=c(0,2)) abline(v=0, h=0, col="grey", lwd=.7) points(mu, ARL, pch=5) lines(mu_, p.ARL_, col="blue") points(mu, p.ARL, pch=18, col ="blue") legend("topright", c("Known", "Estimated"), col=c("black", "blue"), lty=1, pch=c(5, 18)) ## End(Not run)
Computation of the critical values (similar to alarm limits) for different types of EWMA control charts monitoring normal mean.
xewma.crit(l,L0,mu0=0,zr=0,hs=0,sided="one",limits="fix",r=40,c0=NULL,nmax=10000)
xewma.crit(l,L0,mu0=0,zr=0,hs=0,sided="one",limits="fix",r=40,c0=NULL,nmax=10000)
l |
smoothing parameter lambda of the EWMA control chart. |
L0 |
in-control ARL. |
mu0 |
in-control mean. |
zr |
reflection border for the one-sided chart. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided
two-sided EWMA control chart by choosing |
limits |
distinguishes between different control limits behavior. |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
c0 |
starting value for iteration rule. |
nmax |
maximum number of individual control limit factors for |
xewma.crit
determines the critical values (similar to alarm limits)
for given in-control ARL L0
by applying secant rule and using xewma.arl()
.
Returns a single value which resembles the critical value
c
.
Sven Knoth
S. V. Crowder (1989), Design of exponentially weighted moving average schemes, Journal of Quality Technology 21, 155-162.
xewma.arl
for zero-state ARL computation.
l <- .1 incontrolARL <- c(500,5000,50000) sapply(incontrolARL,l=l,sided="two",xewma.crit,r=35) # accuracy with 35 nodes sapply(incontrolARL,l=l,sided="two",xewma.crit) # accuracy with 40 nodes sapply(incontrolARL,l=l,sided="two",xewma.crit,r=50) # accuracy with 50 nodes ## Crowder (1989) ## two-sided EWMA control charts with fixed limits l <- c(.05,.1,.15,.2,.25) L0 <- 250 round(sapply(l,L0=L0,sided="two",xewma.crit),digits=2) ## original values are 2.32, 2.55, 2.65, 2.72, and 2.76.
l <- .1 incontrolARL <- c(500,5000,50000) sapply(incontrolARL,l=l,sided="two",xewma.crit,r=35) # accuracy with 35 nodes sapply(incontrolARL,l=l,sided="two",xewma.crit) # accuracy with 40 nodes sapply(incontrolARL,l=l,sided="two",xewma.crit,r=50) # accuracy with 50 nodes ## Crowder (1989) ## two-sided EWMA control charts with fixed limits l <- c(.05,.1,.15,.2,.25) L0 <- 250 round(sapply(l,L0=L0,sided="two",xewma.crit),digits=2) ## original values are 2.32, 2.55, 2.65, 2.72, and 2.76.
Computation of quantiles of the Run Length (RL) for EWMA control charts monitoring normal mean.
xewma.q(l, c, mu, alpha, zr=0, hs=0, sided="two", limits="fix", q=1, r=40) xewma.q.crit(l, L0, mu, alpha, zr=0, hs=0, sided="two", limits="fix", r=40, c.error=1e-12, a.error=1e-9, OUTPUT=FALSE)
xewma.q(l, c, mu, alpha, zr=0, hs=0, sided="two", limits="fix", q=1, r=40) xewma.q.crit(l, L0, mu, alpha, zr=0, hs=0, sided="two", limits="fix", r=40, c.error=1e-12, a.error=1e-9, OUTPUT=FALSE)
l |
smoothing parameter lambda of the EWMA control chart. |
c |
critical value (similar to alarm limit) of the EWMA control chart. |
mu |
true mean. |
alpha |
quantile level. |
zr |
reflection border for the one-sided chart. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided EWMA control chart
by choosing |
limits |
distinguishes between different control limits behavior. |
q |
change point position. For |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
L0 |
in-control quantile value. |
c.error |
error bound for two succeeding values of the critical value during applying the secant rule. |
a.error |
error bound for the quantile level |
OUTPUT |
activate or deactivate additional output. |
Instead of the popular ARL (Average Run Length) quantiles of the EWMA
stopping time (Run Length) are determined. The algorithm is based on
Waldmann's survival function iteration procedure.
If limits
is not "fix"
, then the method presented
in Knoth (2003) is utilized.
Note that for one-sided EWMA charts (sided
="one"
), only
"vacl"
and "stat"
are deployed, while for two-sided ones
(sided
="two"
) also "fir"
, "both"
(combination of "fir"
and "vacl"
), and "Steiner"
are
implemented. For details see Knoth (2004).
Returns a single value which resembles the RL quantile of order q
.
Sven Knoth
F. F. Gan (1993), An optimal design of EWMA control charts based on the median run length, J. Stat. Comput. Simulation 45, 169-184.
S. Knoth (2003), EWMA schemes with non-homogeneous transition kernels, Sequential Analysis 22, 241-255.
S. Knoth (2004), Fast initial response features for EWMA Control Charts, Statistical Papers 46, 47-64.
S. Knoth (2015), Run length quantiles of EWMA control charts monitoring normal mean or/and variance, International Journal of Production Research 53, 4629-4647.
K.-H. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, Appl. Statist. 35, 151-158.
xewma.arl
for zero-state ARL computation of EWMA control charts.
## Gan (1993), two-sided EWMA with fixed control limits ## some values of his Table 1 -- any median RL should be 500 XEWMA.Q <- Vectorize("xewma.q", c("l", "c")) G.lambda <- c(.05, .1, .15, .2, .25) G.h <- c(.441, .675, .863, 1.027, 1.177) MEDIAN <- ceiling(XEWMA.Q(G.lambda, G.h/sqrt(G.lambda/(2-G.lambda)), 0, .5, sided="two")) print(cbind(G.lambda, MEDIAN)) ## increase accuracy of thresholds # (i) calculate threshold for given in-control median value by # deplyoing secant rule XEWMA.q.crit <- Vectorize("xewma.q.crit", "l") # (ii) re-calculate the thresholds and remove the standardization step L0 <- 500 G.h.new <- XEWMA.q.crit(G.lambda, L0, 0, .5, sided="two") G.h.new <- round(G.h.new * sqrt(G.lambda/(2-G.lambda)), digits=5) # (iii) compare Gan's original values and the new ones with 5 digits print(cbind(G.lambda, G.h.new, G.h)) # (iv) calculate the new medians MEDIAN <- ceiling(XEWMA.Q(G.lambda, G.h.new/sqrt(G.lambda/(2-G.lambda)), 0, .5, sided="two")) print(cbind(G.lambda, MEDIAN))
## Gan (1993), two-sided EWMA with fixed control limits ## some values of his Table 1 -- any median RL should be 500 XEWMA.Q <- Vectorize("xewma.q", c("l", "c")) G.lambda <- c(.05, .1, .15, .2, .25) G.h <- c(.441, .675, .863, 1.027, 1.177) MEDIAN <- ceiling(XEWMA.Q(G.lambda, G.h/sqrt(G.lambda/(2-G.lambda)), 0, .5, sided="two")) print(cbind(G.lambda, MEDIAN)) ## increase accuracy of thresholds # (i) calculate threshold for given in-control median value by # deplyoing secant rule XEWMA.q.crit <- Vectorize("xewma.q.crit", "l") # (ii) re-calculate the thresholds and remove the standardization step L0 <- 500 G.h.new <- XEWMA.q.crit(G.lambda, L0, 0, .5, sided="two") G.h.new <- round(G.h.new * sqrt(G.lambda/(2-G.lambda)), digits=5) # (iii) compare Gan's original values and the new ones with 5 digits print(cbind(G.lambda, G.h.new, G.h)) # (iv) calculate the new medians MEDIAN <- ceiling(XEWMA.Q(G.lambda, G.h.new/sqrt(G.lambda/(2-G.lambda)), 0, .5, sided="two")) print(cbind(G.lambda, MEDIAN))
Computation of quantiles of the Run Length (RL) for EWMA control charts monitoring normal mean if the in-control mean, standard deviation, or both are estimated by a pre run.
xewma.q.prerun(l, c, mu, p, zr=0, hs=0, sided="two", limits="fix", q=1, size=100, df=NULL, estimated="mu", qm.mu=30, qm.sigma=30, truncate=1e-10, bound=1e-10) xewma.q.crit.prerun(l, L0, mu, p, zr=0, hs=0, sided="two", limits="fix", size=100, df=NULL, estimated="mu", qm.mu=30, qm.sigma=30, truncate=1e-10, bound=1e-10, c.error=1e-10, p.error=1e-9, OUTPUT=FALSE)
xewma.q.prerun(l, c, mu, p, zr=0, hs=0, sided="two", limits="fix", q=1, size=100, df=NULL, estimated="mu", qm.mu=30, qm.sigma=30, truncate=1e-10, bound=1e-10) xewma.q.crit.prerun(l, L0, mu, p, zr=0, hs=0, sided="two", limits="fix", size=100, df=NULL, estimated="mu", qm.mu=30, qm.sigma=30, truncate=1e-10, bound=1e-10, c.error=1e-10, p.error=1e-9, OUTPUT=FALSE)
l |
smoothing parameter lambda of the EWMA control chart. |
c |
critical value (similar to alarm limit) of the EWMA control chart. |
mu |
true mean shift. |
p |
quantile level. |
zr |
reflection border for the one-sided chart. |
hs |
so-called headstart (give fast initial response). |
sided |
distinguish between one- and two-sided EWMA control chart
by choosing |
limits |
distinguish between different control limits behavior. |
q |
change point position. For |
size |
pre run sample size. |
df |
Degrees of freedom of the pre run variance estimator. Typically it is simply |
estimated |
name the parameter to be estimated within the |
qm.mu |
number of quadrature nodes for convoluting the mean uncertainty. |
qm.sigma |
number of quadrature nodes for convoluting the standard deviation uncertainty. |
truncate |
size of truncated tail. |
bound |
control when the geometric tail kicks in; the larger the quicker and less accurate; |
L0 |
in-control quantile value. |
c.error |
error bound for two succeeding values of the critical value during applying the secant rule. |
p.error |
error bound for the quantile level |
OUTPUT |
activate or deactivate additional output. |
Essentially, the ARL function xewma.q
is convoluted with the
distribution of the sample mean, standard deviation or both.
For details see Jones/Champ/Rigdon (2001) and Knoth (2014?).
Returns a single value which resembles the RL quantile of order q
.
Sven Knoth
L. A. Jones, C. W. Champ, S. E. Rigdon (2001), The performance of exponentially weighted moving average charts with estimated parameters, Technometrics 43, 156-167.
S. Knoth (2003), EWMA schemes with non-homogeneous transition kernels, Sequential Analysis 22, 241-255.
S. Knoth (2004), Fast initial response features for EWMA Control Charts, Statistical Papers 46, 47-64.
S. Knoth (2014?), tbd, tbd, tbd-tbd.
K.-H. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, Appl. Statist. 35, 151-158.
xewma.q
for the usual RL quantiles computation of EWMA control charts.
## Jones/Champ/Rigdon (2001) c4m <- function(m, n) sqrt(2)*gamma( (m*(n-1)+1)/2 )/sqrt( m*(n-1) )/gamma( m*(n-1)/2 ) n <- 5 # sample size m <- 20 # pre run with 20 samples of size n = 5 C4m <- c4m(m, n) # needed for bias correction # Table 1, 3rd column lambda <- 0.2 L <- 2.636 xewma.Q <- Vectorize("xewma.q", "mu") xewma.Q.prerun <- Vectorize("xewma.q.prerun", "mu") mu <- c(0, .25, .5, 1, 1.5, 2) Q1 <- ceiling(xewma.Q(lambda, L, mu, 0.1, sided="two")) Q2 <- ceiling(xewma.Q(lambda, L, mu, 0.5, sided="two")) Q3 <- ceiling(xewma.Q(lambda, L, mu, 0.9, sided="two")) cbind(mu, Q1, Q2, Q3) ## Not run: p.Q1 <- xewma.Q.prerun(lambda, L/C4m, mu, 0.1, sided="two", size=m, df=m*(n-1), estimated="both") p.Q2 <- xewma.Q.prerun(lambda, L/C4m, mu, 0.5, sided="two", size=m, df=m*(n-1), estimated="both") p.Q3 <- xewma.Q.prerun(lambda, L/C4m, mu, 0.9, sided="two", size=m, df=m*(n-1), estimated="both") cbind(mu, p.Q1, p.Q2, p.Q3) ## End(Not run) ## original values are # mu Q1 Q2 Q3 p.Q1 p.Q2 p.Q3 # 0.00 25 140 456 13 73 345 # 0.25 12 56 174 9 46 253 # 0.50 7 20 56 6 20 101 # 1.00 4 7 15 3 7 18 # 1.50 3 4 7 2 4 8 # 2.00 2 3 5 2 3 5
## Jones/Champ/Rigdon (2001) c4m <- function(m, n) sqrt(2)*gamma( (m*(n-1)+1)/2 )/sqrt( m*(n-1) )/gamma( m*(n-1)/2 ) n <- 5 # sample size m <- 20 # pre run with 20 samples of size n = 5 C4m <- c4m(m, n) # needed for bias correction # Table 1, 3rd column lambda <- 0.2 L <- 2.636 xewma.Q <- Vectorize("xewma.q", "mu") xewma.Q.prerun <- Vectorize("xewma.q.prerun", "mu") mu <- c(0, .25, .5, 1, 1.5, 2) Q1 <- ceiling(xewma.Q(lambda, L, mu, 0.1, sided="two")) Q2 <- ceiling(xewma.Q(lambda, L, mu, 0.5, sided="two")) Q3 <- ceiling(xewma.Q(lambda, L, mu, 0.9, sided="two")) cbind(mu, Q1, Q2, Q3) ## Not run: p.Q1 <- xewma.Q.prerun(lambda, L/C4m, mu, 0.1, sided="two", size=m, df=m*(n-1), estimated="both") p.Q2 <- xewma.Q.prerun(lambda, L/C4m, mu, 0.5, sided="two", size=m, df=m*(n-1), estimated="both") p.Q3 <- xewma.Q.prerun(lambda, L/C4m, mu, 0.9, sided="two", size=m, df=m*(n-1), estimated="both") cbind(mu, p.Q1, p.Q2, p.Q3) ## End(Not run) ## original values are # mu Q1 Q2 Q3 p.Q1 p.Q2 p.Q3 # 0.00 25 140 456 13 73 345 # 0.25 12 56 174 9 46 253 # 0.50 7 20 56 6 20 101 # 1.00 4 7 15 3 7 18 # 1.50 3 4 7 2 4 8 # 2.00 2 3 5 2 3 5
Computation of the survival function of the Run Length (RL) for EWMA control charts monitoring normal mean.
xewma.sf(l, c, mu, n, zr=0, hs=0, sided="one", limits="fix", q=1, r=40)
xewma.sf(l, c, mu, n, zr=0, hs=0, sided="one", limits="fix", q=1, r=40)
l |
smoothing parameter lambda of the EWMA control chart. |
c |
critical value (similar to alarm limit) of the EWMA control chart. |
mu |
true mean. |
n |
calculate sf up to value |
zr |
reflection border for the one-sided chart. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided EWMA control chart
by choosing |
limits |
distinguishes between different control limits behavior. |
q |
change point position. For |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
The survival function P(L>n) and derived from it also the cdf P(L<=n) and the pmf P(L=n) illustrate
the distribution of the EWMA run length. For large n the geometric tail could be exploited. That is,
with reasonable large n the complete distribution is characterized.
The algorithm is based on Waldmann's survival function iteration procedure.
For varying limits and for change points after 1 the algorithm from Knoth (2004) is applied.
Note that for one-sided EWMA charts (sided
="one"
), only
"vacl"
and "stat"
are deployed, while for two-sided ones
(sided
="two"
) also "fir"
, "both"
(combination of "fir"
and "vacl"
), and "Steiner"
are implemented.
For details see Knoth (2004).
Returns a vector which resembles the survival function up to a certain point.
Sven Knoth
F. F. Gan (1993), An optimal design of EWMA control charts based on the median run length, J. Stat. Comput. Simulation 45, 169-184.
S. Knoth (2003), EWMA schemes with non-homogeneous transition kernels, Sequential Analysis 22, 241-255.
S. Knoth (2004), Fast initial response features for EWMA Control Charts, Statistical Papers 46, 47-64.
K.-H. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, Appl. Statist. 35, 151-158.
xewma.arl
for zero-state ARL computation of EWMA control charts.
## Gan (1993), two-sided EWMA with fixed control limits ## some values of his Table 1 -- any median RL should be 500 G.lambda <- c(.05, .1, .15, .2, .25) G.h <- c(.441, .675, .863, 1.027, 1.177)/sqrt(G.lambda/(2-G.lambda)) for ( i in 1:length(G.lambda) ) { SF <- xewma.sf(G.lambda[i], G.h[i], 0, 1000) if (i==1) plot(1:length(SF), SF, type="l", xlab="n", ylab="P(L>n)") else lines(1:length(SF), SF, col=i) }
## Gan (1993), two-sided EWMA with fixed control limits ## some values of his Table 1 -- any median RL should be 500 G.lambda <- c(.05, .1, .15, .2, .25) G.h <- c(.441, .675, .863, 1.027, 1.177)/sqrt(G.lambda/(2-G.lambda)) for ( i in 1:length(G.lambda) ) { SF <- xewma.sf(G.lambda[i], G.h[i], 0, 1000) if (i==1) plot(1:length(SF), SF, type="l", xlab="n", ylab="P(L>n)") else lines(1:length(SF), SF, col=i) }
Computation of the survival function of the Run Length (RL) for EWMA control charts monitoring normal mean if the in-control mean, standard deviation, or both are estimated by a pre run.
xewma.sf.prerun(l, c, mu, n, zr=0, hs=0, sided="one", limits="fix", q=1, size=100, df=NULL, estimated="mu", qm.mu=30, qm.sigma=30, truncate=1e-10, tail_approx=TRUE, bound=1e-10)
xewma.sf.prerun(l, c, mu, n, zr=0, hs=0, sided="one", limits="fix", q=1, size=100, df=NULL, estimated="mu", qm.mu=30, qm.sigma=30, truncate=1e-10, tail_approx=TRUE, bound=1e-10)
l |
smoothing parameter lambda of the EWMA control chart. |
c |
critical value (similar to alarm limit) of the EWMA control chart. |
mu |
true mean. |
n |
calculate sf up to value |
zr |
reflection border for the one-sided chart. |
hs |
so-called headstart (give fast initial response). |
sided |
distinguish between one- and two-sided EWMA control chart
by choosing |
limits |
distinguish between different control limits behavior. |
q |
change point position. For |
size |
pre run sample size. |
df |
degrees of freedom of the pre run variance estimator. Typically it is simply |
estimated |
name the parameter to be estimated within the |
qm.mu |
number of quadrature nodes for convoluting the mean uncertainty. |
qm.sigma |
number of quadrature nodes for convoluting the standard deviation uncertainty. |
truncate |
size of truncated tail. |
tail_approx |
Controls whether the geometric tail approximation is used (is faster) or not. |
bound |
control when the geometric tail kicks in; the larger the quicker and less accurate; |
The survival function P(L>n) and derived from it also the cdf P(L<=n) and the pmf P(L=n) illustrate the distribution of the EWMA run length...
Returns a vector which resembles the survival function up to a certain point.
Sven Knoth
F. F. Gan (1993), An optimal design of EWMA control charts based on the median run length, J. Stat. Comput. Simulation 45, 169-184.
S. Knoth (2003), EWMA schemes with non-homogeneous transition kernels, Sequential Analysis 22, 241-255.
S. Knoth (2004), Fast initial response features for EWMA Control Charts, Statistical Papers 46, 47-64.
L. A. Jones, C. W. Champ, S. E. Rigdon (2001), The performance of exponentially weighted moving average charts with estimated parameters, Technometrics 43, 156-167.
K.-H. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, Appl. Statist. 35, 151-158.
xewma.sf
for the RL survival function of EWMA control charts
w/o pre run uncertainty.
## Jones/Champ/Rigdon (2001) c4m <- function(m, n) sqrt(2)*gamma( (m*(n-1)+1)/2 )/sqrt( m*(n-1) )/gamma( m*(n-1)/2 ) n <- 5 # sample size # Figure 6, subfigure r=0.1 lambda <- 0.1 L <- 2.454 CDF0 <- 1 - xewma.sf(lambda, L, 0, 600, sided="two") m <- 10 # pre run size CDF1 <- 1 - xewma.sf.prerun(lambda, L/c4m(m,n), 0, 600, sided="two", size=m, df=m*(n-1), estimated="both") m <- 20 CDF2 <- 1 - xewma.sf.prerun(lambda, L/c4m(m,n), 0, 600, sided="two", size=m, df=m*(n-1), estimated="both") m <- 50 CDF3 <- 1 - xewma.sf.prerun(lambda, L/c4m(m,n), 0, 600, sided="two", size=m, df=m*(n-1), estimated="both") plot(CDF0, type="l", xlab="t", ylab=expression(P(T<=t)), xlim=c(0,500), ylim=c(0,1)) abline(v=0, h=c(0,1), col="grey", lwd=.7) points((1:5)*100, CDF0[(1:5)*100], pch=18) lines(CDF1, col="blue") points((1:5)*100, CDF1[(1:5)*100], pch=2, col="blue") lines(CDF2, col="red") points((1:5)*100, CDF2[(1:5)*100], pch=16, col="red") lines(CDF3, col="green") points((1:5)*100, CDF3[(1:5)*100], pch=5, col="green") legend("bottomright", c("Known", "m=10, n=5", "m=20, n=5", "m=50, n=5"), col=c("black", "blue", "red", "green"), pch=c(18, 2, 16, 5), lty=1)
## Jones/Champ/Rigdon (2001) c4m <- function(m, n) sqrt(2)*gamma( (m*(n-1)+1)/2 )/sqrt( m*(n-1) )/gamma( m*(n-1)/2 ) n <- 5 # sample size # Figure 6, subfigure r=0.1 lambda <- 0.1 L <- 2.454 CDF0 <- 1 - xewma.sf(lambda, L, 0, 600, sided="two") m <- 10 # pre run size CDF1 <- 1 - xewma.sf.prerun(lambda, L/c4m(m,n), 0, 600, sided="two", size=m, df=m*(n-1), estimated="both") m <- 20 CDF2 <- 1 - xewma.sf.prerun(lambda, L/c4m(m,n), 0, 600, sided="two", size=m, df=m*(n-1), estimated="both") m <- 50 CDF3 <- 1 - xewma.sf.prerun(lambda, L/c4m(m,n), 0, 600, sided="two", size=m, df=m*(n-1), estimated="both") plot(CDF0, type="l", xlab="t", ylab=expression(P(T<=t)), xlim=c(0,500), ylim=c(0,1)) abline(v=0, h=c(0,1), col="grey", lwd=.7) points((1:5)*100, CDF0[(1:5)*100], pch=18) lines(CDF1, col="blue") points((1:5)*100, CDF1[(1:5)*100], pch=2, col="blue") lines(CDF2, col="red") points((1:5)*100, CDF2[(1:5)*100], pch=16, col="red") lines(CDF3, col="green") points((1:5)*100, CDF3[(1:5)*100], pch=5, col="green") legend("bottomright", c("Known", "m=10, n=5", "m=20, n=5", "m=50, n=5"), col=c("black", "blue", "red", "green"), pch=c(18, 2, 16, 5), lty=1)
Computation of the steady-state Average Run Length (ARL) for Shiryaev-Roberts schemes monitoring normal mean.
xgrsr.ad(k, g, mu1, mu0 = 0, zr = 0, sided = "one", MPT = FALSE, r = 30)
xgrsr.ad(k, g, mu1, mu0 = 0, zr = 0, sided = "one", MPT = FALSE, r = 30)
k |
reference value of the Shiryaev-Roberts scheme. |
g |
control limit (alarm threshold) of Shiryaev-Roberts scheme. |
mu1 |
out-of-control mean. |
mu0 |
in-control mean. |
zr |
reflection border to enable the numerical algorithms used here. |
sided |
distinguishes between one- and two-sided schemes by choosing
|
MPT |
switch between the old implementation ( |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
xgrsr.ad
determines the steady-state Average Run Length (ARL) by numerically
solving the related ARL integral equation by means of the Nystroem method
based on Gauss-Legendre quadrature.
Returns a single value which resembles the steady-state ARL.
Sven Knoth
S. Knoth (2006), The art of evaluating monitoring schemes – how to measure the performance of control charts? S. Lenz, H. & Wilrich, P. (ed.), Frontiers in Statistical Quality Control 8, Physica Verlag, Heidelberg, Germany, 74-99.
G. Moustakides, A. Polunchenko, A. Tartakovsky (2009), Numerical comparison of CUSUM and Shiryaev-Roberts procedures for detectin changes in distributions, Communications in Statistics: Theory and Methods 38, 3225-3239.
xewma.arl
and xcusum-arl
for zero-state ARL computation of EWMA and CUSUM control charts,
respectively, and xgrsr.arl
for the zero-state ARL.
## Small study to identify appropriate reflection border to mimic unreflected schemes k <- .5 g <- log(390) zrs <- -(0:10) ZRxgrsr.ad <- Vectorize(xgrsr.ad, "zr") ads <- ZRxgrsr.ad(k, g, 0, zr=zrs) data.frame(zrs, ads) ## Table 2 from Knoth (2006) ## original values are # mu arl # 0 689 # 0.5 30 # 1 8.9 # 1.5 5.1 # 2 3.6 # 2.5 2.8 # 3 2.4 # k <- .5 g <- log(390) zr <- -5 # see first example mus <- (0:6)/2 Mxgrsr.ad <- Vectorize(xgrsr.ad, "mu1") ads <- round(Mxgrsr.ad(k, g, mus, zr=zr), digits=1) data.frame(mus, ads) ## Table 4 from Moustakides et al. (2009) ## original values are # gamma A STADD/steady-state ARL # 50 28.02 4.37 # 100 56.04 5.46 # 500 280.19 8.33 # 1000 560.37 9.64 # 5000 2801.75 12.79 # 10000 5603.7 14.17 Gxgrsr.ad <- Vectorize("xgrsr.ad", "g") As <- c(28.02, 56.04, 280.19, 560.37, 2801.75, 5603.7) gs <- log(As) theta <- 1 zr <- -6 ads <- round(Gxgrsr.ad(theta/2, gs, theta, zr=zr, r=100), digits=2) data.frame(As, ads)
## Small study to identify appropriate reflection border to mimic unreflected schemes k <- .5 g <- log(390) zrs <- -(0:10) ZRxgrsr.ad <- Vectorize(xgrsr.ad, "zr") ads <- ZRxgrsr.ad(k, g, 0, zr=zrs) data.frame(zrs, ads) ## Table 2 from Knoth (2006) ## original values are # mu arl # 0 689 # 0.5 30 # 1 8.9 # 1.5 5.1 # 2 3.6 # 2.5 2.8 # 3 2.4 # k <- .5 g <- log(390) zr <- -5 # see first example mus <- (0:6)/2 Mxgrsr.ad <- Vectorize(xgrsr.ad, "mu1") ads <- round(Mxgrsr.ad(k, g, mus, zr=zr), digits=1) data.frame(mus, ads) ## Table 4 from Moustakides et al. (2009) ## original values are # gamma A STADD/steady-state ARL # 50 28.02 4.37 # 100 56.04 5.46 # 500 280.19 8.33 # 1000 560.37 9.64 # 5000 2801.75 12.79 # 10000 5603.7 14.17 Gxgrsr.ad <- Vectorize("xgrsr.ad", "g") As <- c(28.02, 56.04, 280.19, 560.37, 2801.75, 5603.7) gs <- log(As) theta <- 1 zr <- -6 ads <- round(Gxgrsr.ad(theta/2, gs, theta, zr=zr, r=100), digits=2) data.frame(As, ads)
Computation of the (zero-state) Average Run Length (ARL) for Shiryaev-Roberts schemes monitoring normal mean.
xgrsr.arl(k, g, mu, zr = 0, hs=NULL, sided = "one", q = 1, MPT = FALSE, r = 30)
xgrsr.arl(k, g, mu, zr = 0, hs=NULL, sided = "one", q = 1, MPT = FALSE, r = 30)
k |
reference value of the Shiryaev-Roberts scheme. |
g |
control limit (alarm threshold) of Shiryaev-Roberts scheme. |
mu |
true mean. |
zr |
reflection border to enable the numerical algorithms used here. |
hs |
so-called headstart (enables fast initial response). If |
sided |
distinguishes between one- and two-sided schemes by choosing
|
q |
change point position. For |
MPT |
switch between the old implementation ( |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
xgrsr.arl
determines the Average Run Length (ARL) by numerically
solving the related ARL integral equation by means of the Nystroem method
based on Gauss-Legendre quadrature.
Returns a vector of length q
which resembles the ARL and the sequence of conditional expected delays for
q
=1 and q
>1, respectively.
Sven Knoth
S. Knoth (2006), The art of evaluating monitoring schemes – how to measure the performance of control charts? S. Lenz, H. & Wilrich, P. (ed.), Frontiers in Statistical Quality Control 8, Physica Verlag, Heidelberg, Germany, 74-99.
G. Moustakides, A. Polunchenko, A. Tartakovsky (2009), Numerical comparison of CUSUM and Shiryaev-Roberts procedures for detecting changes in distributions, Communications in Statistics: Theory and Methods 38, 3225-3239.
xewma.arl
and xcusum-arl
for zero-state ARL computation of EWMA and CUSUM control charts,
respectively, and xgrsr.ad
for the steady-state ARL.
## Small study to identify appropriate reflection border to mimic unreflected schemes k <- .5 g <- log(390) zrs <- -(0:10) ZRxgrsr.arl <- Vectorize(xgrsr.arl, "zr") arls <- ZRxgrsr.arl(k, g, 0, zr=zrs) data.frame(zrs, arls) ## Table 2 from Knoth (2006) ## original values are # mu arl # 0 697 # 0.5 33 # 1 10.4 # 1.5 6.2 # 2 4.4 # 2.5 3.5 # 3 2.9 # k <- .5 g <- log(390) zr <- -5 # see first example mus <- (0:6)/2 Mxgrsr.arl <- Vectorize(xgrsr.arl, "mu") arls <- round(Mxgrsr.arl(k, g, mus, zr=zr), digits=1) data.frame(mus, arls) XGRSR.arl <- Vectorize("xgrsr.arl", "g") zr <- -6 ## Table 2 from Moustakides et al. (2009) ## original values are # gamma A ARL/E_infty(L) SADD/E_1(L) # 50 47.17 50.29 41.40 # 100 94.34 100.28 72.32 # 500 471.70 500.28 209.44 # 1000 943.41 1000.28 298.50 # 5000 4717.04 5000.24 557.87 #10000 9434.08 10000.17 684.17 theta <- .1 As2 <- c(47.17, 94.34, 471.7, 943.41, 4717.04, 9434.08) gs2 <- log(As2) arls0 <- round(XGRSR.arl(theta/2, gs2, 0, zr=-5, r=300, MPT=TRUE), digits=2) arls1 <- round(XGRSR.arl(theta/2, gs2, theta, zr=-5, r=300, MPT=TRUE), digits=2) data.frame(As2, arls0, arls1) ## Table 3 from Moustakides et al. (2009) ## original values are # gamma A ARL/E_infty(L) SADD/E_1(L) # 50 37.38 49.45 12.30 # 100 74.76 99.45 16.60 # 500 373.81 499.45 28.05 # 1000 747.62 999.45 33.33 # 5000 3738.08 4999.45 45.96 #10000 7476.15 9999.24 51.49 theta <- .5 As3 <- c(37.38, 74.76, 373.81, 747.62, 3738.08, 7476.15) gs3 <- log(As3) arls0 <- round(XGRSR.arl(theta/2, gs3, 0, zr=-5, r=70, MPT=TRUE), digits=2) arls1 <- round(XGRSR.arl(theta/2, gs3, theta, zr=-5, r=70, MPT=TRUE), digits=2) data.frame(As3, arls0, arls1) ## Table 4 from Moustakides et al. (2009) ## original values are # gamma A ARL/E_infty(L) SADD/E_1(L) # 50 28.02 49.78 4.98 # 100 56.04 99.79 6.22 # 500 280.19 499.79 9.30 # 1000 560.37 999.79 10.66 # 5000 2801.85 5000.93 13.86 #10000 5603.70 9999.87 15.24 theta <- 1 As4 <- c(28.02, 56.04, 280.19, 560.37, 2801.85, 5603.7) gs4 <- log(As4) arls0 <- round(XGRSR.arl(theta/2, gs4, 0, zr=-6, r=40, MPT=TRUE), digits=2) arls1 <- round(XGRSR.arl(theta/2, gs4, theta, zr=-6, r=40, MPT=TRUE), digits=2) data.frame(As4, arls0, arls1)
## Small study to identify appropriate reflection border to mimic unreflected schemes k <- .5 g <- log(390) zrs <- -(0:10) ZRxgrsr.arl <- Vectorize(xgrsr.arl, "zr") arls <- ZRxgrsr.arl(k, g, 0, zr=zrs) data.frame(zrs, arls) ## Table 2 from Knoth (2006) ## original values are # mu arl # 0 697 # 0.5 33 # 1 10.4 # 1.5 6.2 # 2 4.4 # 2.5 3.5 # 3 2.9 # k <- .5 g <- log(390) zr <- -5 # see first example mus <- (0:6)/2 Mxgrsr.arl <- Vectorize(xgrsr.arl, "mu") arls <- round(Mxgrsr.arl(k, g, mus, zr=zr), digits=1) data.frame(mus, arls) XGRSR.arl <- Vectorize("xgrsr.arl", "g") zr <- -6 ## Table 2 from Moustakides et al. (2009) ## original values are # gamma A ARL/E_infty(L) SADD/E_1(L) # 50 47.17 50.29 41.40 # 100 94.34 100.28 72.32 # 500 471.70 500.28 209.44 # 1000 943.41 1000.28 298.50 # 5000 4717.04 5000.24 557.87 #10000 9434.08 10000.17 684.17 theta <- .1 As2 <- c(47.17, 94.34, 471.7, 943.41, 4717.04, 9434.08) gs2 <- log(As2) arls0 <- round(XGRSR.arl(theta/2, gs2, 0, zr=-5, r=300, MPT=TRUE), digits=2) arls1 <- round(XGRSR.arl(theta/2, gs2, theta, zr=-5, r=300, MPT=TRUE), digits=2) data.frame(As2, arls0, arls1) ## Table 3 from Moustakides et al. (2009) ## original values are # gamma A ARL/E_infty(L) SADD/E_1(L) # 50 37.38 49.45 12.30 # 100 74.76 99.45 16.60 # 500 373.81 499.45 28.05 # 1000 747.62 999.45 33.33 # 5000 3738.08 4999.45 45.96 #10000 7476.15 9999.24 51.49 theta <- .5 As3 <- c(37.38, 74.76, 373.81, 747.62, 3738.08, 7476.15) gs3 <- log(As3) arls0 <- round(XGRSR.arl(theta/2, gs3, 0, zr=-5, r=70, MPT=TRUE), digits=2) arls1 <- round(XGRSR.arl(theta/2, gs3, theta, zr=-5, r=70, MPT=TRUE), digits=2) data.frame(As3, arls0, arls1) ## Table 4 from Moustakides et al. (2009) ## original values are # gamma A ARL/E_infty(L) SADD/E_1(L) # 50 28.02 49.78 4.98 # 100 56.04 99.79 6.22 # 500 280.19 499.79 9.30 # 1000 560.37 999.79 10.66 # 5000 2801.85 5000.93 13.86 #10000 5603.70 9999.87 15.24 theta <- 1 As4 <- c(28.02, 56.04, 280.19, 560.37, 2801.85, 5603.7) gs4 <- log(As4) arls0 <- round(XGRSR.arl(theta/2, gs4, 0, zr=-6, r=40, MPT=TRUE), digits=2) arls1 <- round(XGRSR.arl(theta/2, gs4, theta, zr=-6, r=40, MPT=TRUE), digits=2) data.frame(As4, arls0, arls1)
Computation of the alarm thresholds (alarm limits) for Shiryaev-Roberts schemes monitoring normal mean.
xgrsr.crit(k, L0, mu0 = 0, zr = 0, hs = NULL, sided = "one", MPT = FALSE, r = 30)
xgrsr.crit(k, L0, mu0 = 0, zr = 0, hs = NULL, sided = "one", MPT = FALSE, r = 30)
k |
reference value of the Shiryaev-Roberts scheme. |
L0 |
in-control ARL. |
mu0 |
in-control mean. |
zr |
reflection border to enable the numerical algorithms used here. |
hs |
so-called headstart (enables fast initial response). If |
sided |
distinguishes between one- and two-sided schemes by choosing
|
MPT |
switch between the old implementation ( |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
xgrsr.crit
determines the alarm threshold (alarm limit)
for given in-control ARL L0
by applying secant rule and using xgrsr.arl()
.
Returns a single value which resembles the alarm limit g
.
Sven Knoth
G. Moustakides, A. Polunchenko, A. Tartakovsky (2009), Numerical comparison of CUSUM and Shiryaev-Roberts procedures for detecting changes in distributions, Communications in Statistics: Theory and Methods 38, 3225-3239.r.
xgrsr.arl
for zero-state ARL computation.
## Table 4 from Moustakides et al. (2009) ## original values are # gamma/L0 A/exp(g) # 50 28.02 # 100 56.04 # 500 280.19 # 1000 560.37 # 5000 2801.75 # 10000 5603.7 theta <- 1 zr <- -6 r <- 100 Lxgrsr.crit <- Vectorize("xgrsr.crit", "L0") L0s <- c(50, 100, 500, 1000, 5000, 10000) gs <- Lxgrsr.crit(theta/2, L0s, zr=zr, r=r) data.frame(L0s, gs, A=round(exp(gs), digits=2))
## Table 4 from Moustakides et al. (2009) ## original values are # gamma/L0 A/exp(g) # 50 28.02 # 100 56.04 # 500 280.19 # 1000 560.37 # 5000 2801.75 # 10000 5603.7 theta <- 1 zr <- -6 r <- 100 Lxgrsr.crit <- Vectorize("xgrsr.crit", "L0") L0s <- c(50, 100, 500, 1000, 5000, 10000) gs <- Lxgrsr.crit(theta/2, L0s, zr=zr, r=r) data.frame(L0s, gs, A=round(exp(gs), digits=2))
Computation of the (zero-state) Average Run Length (ARL)
for different types of simultaneous EWMA control charts
(based on the sample mean and the sample variance )
monitoring normal mean and variance.
xsewma.arl(lx, cx, ls, csu, df, mu, sigma, hsx=0, Nx=40, csl=0, hss=1, Ns=40, s2.on=TRUE, sided="upper", qm=30)
xsewma.arl(lx, cx, ls, csu, df, mu, sigma, hsx=0, Nx=40, csl=0, hss=1, Ns=40, s2.on=TRUE, sided="upper", qm=30)
lx |
smoothing parameter lambda of the two-sided mean EWMA chart. |
cx |
control limit of the two-sided mean EWMA control chart. |
ls |
smoothing parameter lambda of the variance EWMA chart. |
csu |
upper control limit of the variance EWMA control chart. |
df |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
mu |
true mean. |
sigma |
true standard deviation. |
hsx |
so-called headstart (enables fast initial response) of the mean chart – do not confuse with the true FIR feature considered in xewma.arl; will be updated. |
Nx |
dimension of the approximating matrix of the mean chart. |
csl |
lower control limit of the variance EWMA control chart; default value is 0;
not considered if |
hss |
headstart (enables fast initial response) of the variance chart. |
Ns |
dimension of the approximating matrix of the variance chart. |
s2.on |
distinguishes between |
sided |
distinguishes between one- and two-sided two-sided EWMA- |
qm |
number of quadrature nodes used for the collocation integrals. |
xsewma.arl
determines the Average Run Length (ARL) by
an extension of Gan's (derived from ideas already published by Waldmann)
algorithm. The variance EWMA part is treated
similarly to the ARL calculation method
deployed for the single variance EWMA charts in Knoth (2005), that is, by means of
collocation (Chebyshev polynomials). For more details see Knoth (2007).
Returns a single value which resembles the ARL.
Sven Knoth
K. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, J. R. Stat. Soc., Ser. C, Appl. Stat. 35, 151-158.
F. F. Gan (1995), Joint monitoring of process mean and variance using exponentially weighted moving average control charts, Technometrics 37, 446-453.
S. Knoth (2005),
Accurate ARL computation for EWMA- control charts,
Statistics and Computing 15, 341-352.
S. Knoth (2007), Accurate ARL calculation for EWMA control charts monitoring simultaneously normal mean and variance, Sequential Analysis 26, 251-264.
xewma.arl
and sewma.arl
for zero-state ARL computation of
single mean and variance EWMA control charts, respectively.
## Knoth (2007) ## collocation results in Table 1 ## Monte Carlo with 10^9 replicates: 252.307 +/- 0.0078 # process parameters mu <- 0 sigma <- 1 # subgroup size n=5, df=n-1 df <- 4 # lambda of mean chart lx <- .134 # c_mu^* = .345476571 = cx/sqrt(n) * sqrt(lx/(2-lx) cx <- .345476571*sqrt(df+1)/sqrt(lx/(2-lx)) # lambda of variance chart ls <- .1 # c_sigma = .477977 csu <- 1 + .477977 # matrix dimensions for mean and variance part Nx <- 25 Ns <- 25 # mode of variance chart SIDED <- "upper" arl <- xsewma.arl(lx, cx, ls, csu, df, mu, sigma, Nx=Nx, Ns=Ns, sided=SIDED) arl
## Knoth (2007) ## collocation results in Table 1 ## Monte Carlo with 10^9 replicates: 252.307 +/- 0.0078 # process parameters mu <- 0 sigma <- 1 # subgroup size n=5, df=n-1 df <- 4 # lambda of mean chart lx <- .134 # c_mu^* = .345476571 = cx/sqrt(n) * sqrt(lx/(2-lx) cx <- .345476571*sqrt(df+1)/sqrt(lx/(2-lx)) # lambda of variance chart ls <- .1 # c_sigma = .477977 csu <- 1 + .477977 # matrix dimensions for mean and variance part Nx <- 25 Ns <- 25 # mode of variance chart SIDED <- "upper" arl <- xsewma.arl(lx, cx, ls, csu, df, mu, sigma, Nx=Nx, Ns=Ns, sided=SIDED) arl
Computation of the critical values (similar to alarm limits)
for different types of simultaneous EWMA control charts
(based on the sample mean and the sample variance )
monitoring normal mean and variance.
xsewma.crit(lx, ls, L0, df, mu0=0, sigma0=1, cu=NULL, hsx=0, hss=1, s2.on=TRUE, sided="upper", mode="fixed", Nx=30, Ns=40, qm=30)
xsewma.crit(lx, ls, L0, df, mu0=0, sigma0=1, cu=NULL, hsx=0, hss=1, s2.on=TRUE, sided="upper", mode="fixed", Nx=30, Ns=40, qm=30)
lx |
smoothing parameter lambda of the two-sided mean EWMA chart. |
ls |
smoothing parameter lambda of the variance EWMA chart. |
L0 |
in-control ARL. |
mu0 |
in-control mean. |
sigma0 |
in-control standard deviation. |
cu |
for two-sided ( |
hsx |
so-called headstart (enables fast initial response) of the mean chart – do not confuse with the true FIR feature considered in xewma.arl; will be updated. |
hss |
headstart (enables fast initial response) of the variance chart. |
df |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
s2.on |
distinguishes between |
sided |
distinguishes between one- and two-sided two-sided EWMA- |
mode |
only deployed for |
Nx |
dimension of the approximating matrix of the mean chart. |
Ns |
dimension of the approximating matrix of the variance chart. |
qm |
number of quadrature nodes used for the collocation integrals. |
xsewma.crit
determines the critical values (similar to alarm limits)
for given in-control ARL L0
by applying secant rule and using xsewma.arl()
.
In case of sided
="two"
and mode
="unbiased"
a two-dimensional secant rule is applied that also ensures that the
maximum of the ARL function for given standard deviation is attained
at sigma0
. See Knoth (2007) for details and application.
Returns the critical value of the two-sided mean EWMA chart and
the lower and upper controls limit cl
and cu
of the variance EWMA chart.
Sven Knoth
S. Knoth (2007), Accurate ARL calculation for EWMA control charts monitoring simultaneously normal mean and variance, Sequential Analysis 26, 251-264.
xsewma.arl
for calculation of ARL of simultaneous EWMA charts.
## Knoth (2007) ## results in Table 2 # subgroup size n=5, df=n-1 df <- 4 # lambda of mean chart lx <- .134 # lambda of variance chart ls <- .1 # in-control ARL L0 <- 252.3 # matrix dimensions for mean and variance part Nx <- 25 Ns <- 25 # mode of variance chart SIDED <- "upper" crit <- xsewma.crit(lx, ls, L0, df, sided=SIDED, Nx=Nx, Ns=Ns) crit ## output as used in Knoth (2007) crit["cx"]/sqrt(df+1)*sqrt(lx/(2-lx)) crit["cu"] - 1
## Knoth (2007) ## results in Table 2 # subgroup size n=5, df=n-1 df <- 4 # lambda of mean chart lx <- .134 # lambda of variance chart ls <- .1 # in-control ARL L0 <- 252.3 # matrix dimensions for mean and variance part Nx <- 25 Ns <- 25 # mode of variance chart SIDED <- "upper" crit <- xsewma.crit(lx, ls, L0, df, sided=SIDED, Nx=Nx, Ns=Ns) crit ## output as used in Knoth (2007) crit["cx"]/sqrt(df+1)*sqrt(lx/(2-lx)) crit["cu"] - 1
Computation of the critical values (similar to alarm limits)
for different types of simultaneous EWMA control charts
(based on the sample mean and the sample variance )
monitoring normal mean and variance.
xsewma.q(lx, cx, ls, csu, df, alpha, mu, sigma, hsx=0, Nx=40, csl=0, hss=1, Ns=40, sided="upper", qm=30) xsewma.q.crit(lx, ls, L0, alpha, df, mu0=0, sigma0=1, csu=NULL, hsx=0, hss=1, sided="upper", mode="fixed", Nx=20, Ns=40, qm=30, c.error=1e-12, a.error=1e-9)
xsewma.q(lx, cx, ls, csu, df, alpha, mu, sigma, hsx=0, Nx=40, csl=0, hss=1, Ns=40, sided="upper", qm=30) xsewma.q.crit(lx, ls, L0, alpha, df, mu0=0, sigma0=1, csu=NULL, hsx=0, hss=1, sided="upper", mode="fixed", Nx=20, Ns=40, qm=30, c.error=1e-12, a.error=1e-9)
lx |
smoothing parameter lambda of the two-sided mean EWMA chart. |
cx |
control limit of the two-sided mean EWMA control chart. |
ls |
smoothing parameter lambda of the variance EWMA chart. |
csu |
for two-sided ( |
L0 |
in-control RL quantile at level |
df |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
alpha |
quantile level. |
mu |
true mean. |
sigma |
true standard deviation. |
mu0 |
in-control mean. |
sigma0 |
in-control standard deviation. |
hsx |
so-called headstart (enables fast initial response) of the mean chart – do not confuse with the true FIR feature considered in xewma.arl; will be updated. |
Nx |
dimension of the approximating matrix of the mean chart. |
csl |
lower control limit of the variance EWMA control chart; default value is 0;
not considered if |
hss |
headstart (enables fast initial response) of the variance chart. |
Ns |
dimension of the approximating matrix of the variance chart. |
sided |
distinguishes between one- and two-sided two-sided
EWMA- |
mode |
only deployed for |
qm |
number of quadrature nodes used for the collocation integrals. |
c.error |
error bound for two succeeding values of the critical value during applying the secant rule. |
a.error |
error bound for the quantile level |
Instead of the popular ARL (Average Run Length) quantiles of the EWMA
stopping time (Run Length) are determined. The algorithm is based on
Waldmann's survival function iteration procedure and on Knoth (2007).
xsewma.q.crit
determines the critical values (similar to alarm limits)
for given in-control RL quantile L0
at level alpha
by applying secant
rule and using xsewma.sf()
.
In case of sided
="two"
and mode
="unbiased"
a two-dimensional secant rule is applied that also ensures that the
maximum of the RL cdf for given standard deviation is attained at sigma0
.
Returns a single value which resembles the RL quantile of order alpha
and
the critical value of the two-sided mean EWMA chart and
the lower and upper controls limit csl
and csu
of the
variance EWMA chart, respectively.
Sven Knoth
S. Knoth (2007), Accurate ARL calculation for EWMA control charts monitoring simultaneously normal mean and variance, Sequential Analysis 26, 251-264.
xsewma.arl
for calculation of ARL of simultaneous EWMA charts and
xsewma.sf
for the RL survival function.
## will follow
## will follow
Computation of the survival function of the Run Length (RL) for EWMA control charts monitoring simultaneously normal mean and variance.
xsewma.sf(n, lx, cx, ls, csu, df, mu, sigma, hsx=0, Nx=40, csl=0, hss=1, Ns=40, sided="upper", qm=30)
xsewma.sf(n, lx, cx, ls, csu, df, mu, sigma, hsx=0, Nx=40, csl=0, hss=1, Ns=40, sided="upper", qm=30)
n |
calculate sf up to value |
lx |
smoothing parameter lambda of the two-sided mean EWMA chart. |
cx |
control limit of the two-sided mean EWMA control chart. |
ls |
smoothing parameter lambda of the variance EWMA chart. |
csu |
upper control limit of the variance EWMA control chart. |
df |
actual degrees of freedom, corresponds to subgroup size (for known mean it is equal to the subgroup size, for unknown mean it is equal to subgroup size minus one. |
mu |
true mean. |
sigma |
true standard deviation. |
hsx |
so-called headstart (enables fast initial response) of the mean chart – do not confuse with the true FIR feature considered in xewma.arl; will be updated. |
Nx |
dimension of the approximating matrix of the mean chart. |
csl |
lower control limit of the variance EWMA control chart; default value is 0;
not considered if |
hss |
headstart (enables fast initial response) of the variance chart. |
Ns |
dimension of the approximating matrix of the variance chart. |
sided |
distinguishes between one- and two-sided two-sided
EWMA- |
qm |
number of quadrature nodes used for the collocation integrals. |
The survival function P(L>n) and derived from it also the cdf P(L<=n) and the pmf P(L=n) illustrate the distribution of the EWMA run length. For large n the geometric tail could be exploited. That is, with reasonable large n the complete distribution is characterized. The algorithm is based on Waldmann's survival function iteration procedure and on results in Knoth (2007).
Returns a vector which resembles the survival function up to a certain point.
Sven Knoth
S. Knoth (2007), Accurate ARL calculation for EWMA control charts monitoring simultaneously normal mean and variance, Sequential Analysis 26, 251-264.
K.-H. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, Appl. Statist. 35, 151-158.
xsewma.arl
for zero-state ARL computation of simultaneous EWMA
control charts.
## will follow
## will follow
Computation of the (zero-state) Average Run Length (ARL) for modified Shewhart charts deployed to the original AR(1) data.
xshewhart.ar1.arl(alpha, cS, delta=0, N1=50, N2=30)
xshewhart.ar1.arl(alpha, cS, delta=0, N1=50, N2=30)
alpha |
lag 1 correlation of the data. |
cS |
critical value (alias to alarm limit) of the Shewhart control chart. |
delta |
potential shift in the data (in-control mean is zero. |
N1 |
number of quadrature nodes for solving the ARL integral equation, dimension of the resulting linear equation system is |
N2 |
second number of quadrature nodes for combining the probability density function of the first observation following the margin distribution and the solution of the ARL integral equation. |
Following the idea of Schmid (1995), 1- alpha
times the data turns out to be an
EWMA smoothing of the underlying AR(1) residuals. Hence, by combining the solution of
the EWMA ARL integral equation and the stationary distribution of the AR(1) data
(normal distribution is assumed) one gets easily the overall ARL.
It returns a single value resembling the zero-state ARL of a modified Shewhart chart.
Sven Knoth
S. Knoth, W. Schmid (2004). Control charts for time series: A review. In Frontiers in Statistical Quality Control 7, edited by H.-J. Lenz, P.-T. Wilrich, 210-236, Physica-Verlag.
H. Kramer, W. Schmid (2000). The influence of parameter estimation on the ARL of Shewhart type charts for time series. Statistical Papers 41(2), 173-196.
W. Schmid (1995). On the run length of a Shewhart chart for correlated data. Statistical Papers 36(1), 111-130.
xewma.arl
for zero-state ARL computation of EWMA control charts.
## Table 1 in Kramer/Schmid (2000) cS <- 3.09023 a <- seq(0, 4, by=.5) row1 <- row2 <- row3 <- NULL for ( i in 1:length(a) ) { row1 <- c(row1, round(xshewhart.ar1.arl( 0.4, cS, delta=a[i]), digits=2)) row2 <- c(row2, round(xshewhart.ar1.arl( 0.2, cS, delta=a[i]), digits=2)) row3 <- c(row3, round(xshewhart.ar1.arl(-0.2, cS, delta=a[i]), digits=2)) } results <- rbind(row1, row2, row3) results # original values are # row1 515.44 215.48 61.85 21.63 9.19 4.58 2.61 1.71 1.29 # row2 502.56 204.97 56.72 19.13 7.95 3.97 2.33 1.59 1.25 # row3 502.56 201.41 54.05 17.42 6.89 3.37 2.03 1.46 1.20
## Table 1 in Kramer/Schmid (2000) cS <- 3.09023 a <- seq(0, 4, by=.5) row1 <- row2 <- row3 <- NULL for ( i in 1:length(a) ) { row1 <- c(row1, round(xshewhart.ar1.arl( 0.4, cS, delta=a[i]), digits=2)) row2 <- c(row2, round(xshewhart.ar1.arl( 0.2, cS, delta=a[i]), digits=2)) row3 <- c(row3, round(xshewhart.ar1.arl(-0.2, cS, delta=a[i]), digits=2)) } results <- rbind(row1, row2, row3) results # original values are # row1 515.44 215.48 61.85 21.63 9.19 4.58 2.61 1.71 1.29 # row2 502.56 204.97 56.72 19.13 7.95 3.97 2.33 1.59 1.25 # row3 502.56 201.41 54.05 17.42 6.89 3.37 2.03 1.46 1.20
Computation of the (zero-state and steady-state) Average Run Length (ARL) for Shewhart control charts with and without runs rules monitoring normal mean.
xshewhartrunsrules.arl(mu, c = 1, type = "12") xshewhartrunsrules.crit(L0, mu = 0, type = "12") xshewhartrunsrules.ad(mu1, mu0 = 0, c = 1, type = "12") xshewhartrunsrules.matrix(mu, c = 1, type = "12")
xshewhartrunsrules.arl(mu, c = 1, type = "12") xshewhartrunsrules.crit(L0, mu = 0, type = "12") xshewhartrunsrules.ad(mu1, mu0 = 0, c = 1, type = "12") xshewhartrunsrules.matrix(mu, c = 1, type = "12")
mu |
true mean. |
L0 |
pre-defined in-control ARL, that is, determine |
mu1 , mu0
|
for the steady-state ARL two means are specified, mu0 is the in-control one and usually equal to 0 , and mu1 must be given. |
c |
normalizing constant to ensure specific alarming behavior. |
type |
controls the type of Shewhart chart used, seed details section. |
xshewhartrunsrules.arl
determines the zero-state Average Run Length (ARL)
based on the Markov chain approach given in Champ and Woodall (1987).
xshewhartrunsrules.matrix
provides the corresponding
transition matrix that is also used in xDshewhartrunsrules.arl
(ARL for control charting drift).
xshewhartrunsrules.crit
allows to find the normalization constant c
to
attain a fixed in-control ARL. Typically this is needed to calibrate the chart.
With xshewhartrunsrules.ad
the steady-state ARL is calculated.
With the argument type
certain runs rules could be set. The following list gives an overview.
The classical Shewhart chart with +/- 3 c sigma
control limits (c
is typically
equal to 1 and can be changed by the argument c
).
The classic and the following runs rule: 2 of 3 are beyond +/- 2 c sigma
on the same
side of the chart.
The classic and the following runs rule: 4 of 5 are beyond +/- 1 c sigma
on the same
side of the chart.
The classic and the following runs rule: 8 of 8 are on the same side of the chart (referring to the center line).
Returns a single value which resembles the zero-state or steady-state ARL.
xshewhartrunsrules.matrix
returns a matrix.
Sven Knoth
C. W. Champ and W. H. Woodall (1987), Exact results for Shewhart control charts with supplementary runs rules, Technometrics 29, 393-399.
xDshewhartrunsrules.arl
for zero-state ARL of Shewhart control charts
with or without runs rules under drift.
## Champ/Woodall (1987) ## Table 1 mus <- (0:15)/5 Mxshewhartrunsrules.arl <- Vectorize(xshewhartrunsrules.arl, "mu") # standard (1 of 1 beyond 3 sigma) Shewhart chart without runs rules C1 <- round(Mxshewhartrunsrules.arl(mus, type="1"), digits=2) # standard + runs rule: 2 of 3 beyond 2 sigma on the same side C12 <- round(Mxshewhartrunsrules.arl(mus, type="12"), digits=2) # standard + runs rule: 4 of 5 beyond 1 sigma on the same side C13 <- round(Mxshewhartrunsrules.arl(mus, type="13"), digits=2) # standard + runs rule: 8 of 8 on the same side of the center line C14 <- round(Mxshewhartrunsrules.arl(mus, type="14"), digits=2) ## original results are # mus C1 C12 C13 C14 # 0.0 370.40 225.44 166.05 152.73 # 0.2 308.43 177.56 120.70 110.52 # 0.4 200.08 104.46 63.88 59.76 # 0.6 119.67 57.92 33.99 33.64 # 0.8 71.55 33.12 19.78 21.07 # 1.0 43.89 20.01 12.66 14.58 # 1.2 27.82 12.81 8.84 10.90 # 1.4 18.25 8.69 6.62 8.60 # 1.6 12.38 6.21 5.24 7.03 # 1.8 8.69 4.66 4.33 5.85 # 2.0 6.30 3.65 3.68 4.89 # 2.2 4.72 2.96 3.18 4.08 # 2.4 3.65 2.48 2.78 3.38 # 2.6 2.90 2.13 2.43 2.81 # 2.8 2.38 1.87 2.14 2.35 # 3.0 2.00 1.68 1.89 1.99 data.frame(mus, C1, C12, C13, C14) ## plus calibration, i. e. L0=250 (the maximal value for "14" is 255! L0 <- 250 c1 <- xshewhartrunsrules.crit(L0, type = "1") c12 <- xshewhartrunsrules.crit(L0, type = "12") c13 <- xshewhartrunsrules.crit(L0, type = "13") c14 <- xshewhartrunsrules.crit(L0, type = "14") C1 <- round(Mxshewhartrunsrules.arl(mus, c=c1, type="1"), digits=2) C12 <- round(Mxshewhartrunsrules.arl(mus, c=c12, type="12"), digits=2) C13 <- round(Mxshewhartrunsrules.arl(mus, c=c13, type="13"), digits=2) C14 <- round(Mxshewhartrunsrules.arl(mus, c=c14, type="14"), digits=2) data.frame(mus, C1, C12, C13, C14) ## and the steady-state ARL Mxshewhartrunsrules.ad <- Vectorize(xshewhartrunsrules.ad, "mu1") C1 <- round(Mxshewhartrunsrules.ad(mus, c=c1, type="1"), digits=2) C12 <- round(Mxshewhartrunsrules.ad(mus, c=c12, type="12"), digits=2) C13 <- round(Mxshewhartrunsrules.ad(mus, c=c13, type="13"), digits=2) C14 <- round(Mxshewhartrunsrules.ad(mus, c=c14, type="14"), digits=2) data.frame(mus, C1, C12, C13, C14)
## Champ/Woodall (1987) ## Table 1 mus <- (0:15)/5 Mxshewhartrunsrules.arl <- Vectorize(xshewhartrunsrules.arl, "mu") # standard (1 of 1 beyond 3 sigma) Shewhart chart without runs rules C1 <- round(Mxshewhartrunsrules.arl(mus, type="1"), digits=2) # standard + runs rule: 2 of 3 beyond 2 sigma on the same side C12 <- round(Mxshewhartrunsrules.arl(mus, type="12"), digits=2) # standard + runs rule: 4 of 5 beyond 1 sigma on the same side C13 <- round(Mxshewhartrunsrules.arl(mus, type="13"), digits=2) # standard + runs rule: 8 of 8 on the same side of the center line C14 <- round(Mxshewhartrunsrules.arl(mus, type="14"), digits=2) ## original results are # mus C1 C12 C13 C14 # 0.0 370.40 225.44 166.05 152.73 # 0.2 308.43 177.56 120.70 110.52 # 0.4 200.08 104.46 63.88 59.76 # 0.6 119.67 57.92 33.99 33.64 # 0.8 71.55 33.12 19.78 21.07 # 1.0 43.89 20.01 12.66 14.58 # 1.2 27.82 12.81 8.84 10.90 # 1.4 18.25 8.69 6.62 8.60 # 1.6 12.38 6.21 5.24 7.03 # 1.8 8.69 4.66 4.33 5.85 # 2.0 6.30 3.65 3.68 4.89 # 2.2 4.72 2.96 3.18 4.08 # 2.4 3.65 2.48 2.78 3.38 # 2.6 2.90 2.13 2.43 2.81 # 2.8 2.38 1.87 2.14 2.35 # 3.0 2.00 1.68 1.89 1.99 data.frame(mus, C1, C12, C13, C14) ## plus calibration, i. e. L0=250 (the maximal value for "14" is 255! L0 <- 250 c1 <- xshewhartrunsrules.crit(L0, type = "1") c12 <- xshewhartrunsrules.crit(L0, type = "12") c13 <- xshewhartrunsrules.crit(L0, type = "13") c14 <- xshewhartrunsrules.crit(L0, type = "14") C1 <- round(Mxshewhartrunsrules.arl(mus, c=c1, type="1"), digits=2) C12 <- round(Mxshewhartrunsrules.arl(mus, c=c12, type="12"), digits=2) C13 <- round(Mxshewhartrunsrules.arl(mus, c=c13, type="13"), digits=2) C14 <- round(Mxshewhartrunsrules.arl(mus, c=c14, type="14"), digits=2) data.frame(mus, C1, C12, C13, C14) ## and the steady-state ARL Mxshewhartrunsrules.ad <- Vectorize(xshewhartrunsrules.ad, "mu1") C1 <- round(Mxshewhartrunsrules.ad(mus, c=c1, type="1"), digits=2) C12 <- round(Mxshewhartrunsrules.ad(mus, c=c12, type="12"), digits=2) C13 <- round(Mxshewhartrunsrules.ad(mus, c=c13, type="13"), digits=2) C14 <- round(Mxshewhartrunsrules.ad(mus, c=c14, type="14"), digits=2) data.frame(mus, C1, C12, C13, C14)
Computation of the (zero-state) Average Run Length (ARL) for different types of CUSUM control charts monitoring normal mean.
xtcusum.arl(k, h, df, mu, hs = 0, sided="one", mode="tan", r=30)
xtcusum.arl(k, h, df, mu, hs = 0, sided="one", mode="tan", r=30)
k |
reference value of the CUSUM control chart. |
h |
decision interval (alarm limit, threshold) of the CUSUM control chart. |
df |
degrees of freedom – parameter of the t distribution. |
mu |
true mean. |
hs |
so-called headstart (give fast initial response). |
sided |
distinguish between one- and two-sided CUSUM schemes by choosing |
r |
number of quadrature nodes, dimension of the resulting linear equation system is equal to |
mode |
Controls the type of variables substitution that might improve the numerical performance. Currently, |
xtcusum.arl
determines the Average Run Length (ARL) by numerically
solving the related ARL integral equation by means of the Nystroem method
based on Gauss-Legendre quadrature.
Returns a single value which resembles the ARL.
Sven Knoth
A. L. Goel, S. M. Wu (1971), Determination of A.R.L. and a contour nomogram for CUSUM charts to control normal mean, Technometrics 13, 221-230.
D. Brook, D. A. Evans (1972), An approach to the probability distribution of cusum run length, Biometrika 59, 539-548.
J. M. Lucas, R. B. Crosier (1982), Fast initial response for cusum quality-control schemes: Give your cusum a headstart, Technometrics 24, 199-205.
L. C. Vance (1986), Average run lengths of cumulative sum control charts for controlling normal means, Journal of Quality Technology 18, 189-193.
K.-H. Waldmann (1986), Bounds for the distribution of the run length of one-sided and two-sided CUSUM quality control schemes, Technometrics 28, 61-67.
R. B. Crosier (1986), A new two-sided cumulative quality control scheme, Technometrics 28, 187-194.
xtewma.arl
for zero-state ARL computation of EWMA control charts and xtcusum.arl
for the zero-state ARL of CUSUM for normal data.
## will follow
## will follow
Computation of the steady-state Average Run Length (ARL) for different types of EWMA control charts monitoring the mean of t distributed data.
xtewma.ad(l, c, df, mu1, mu0=0, zr=0, z0=0, sided="one", limits="fix", steady.state.mode="conditional", mode="tan", r=40)
xtewma.ad(l, c, df, mu1, mu0=0, zr=0, z0=0, sided="one", limits="fix", steady.state.mode="conditional", mode="tan", r=40)
l |
smoothing parameter lambda of the EWMA control chart. |
c |
critical value (similar to alarm limit) of the EWMA control chart. |
df |
degrees of freedom – parameter of the t distribution. |
mu1 |
in-control mean. |
mu0 |
out-of-control mean. |
zr |
reflection border for the one-sided chart. |
z0 |
restarting value of the EWMA sequence in case of a false alarm in
|
sided |
distinguishes between one- and two-sided two-sided EWMA control
chart by choosing |
limits |
distinguishes between different control limits behavior. |
steady.state.mode |
distinguishes between two steady-state modes – conditional and cyclical. |
mode |
Controls the type of variables substitution that might improve the numerical performance. Currently,
|
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
xtewma.ad
determines the steady-state Average Run Length (ARL)
by numerically solving the related ARL integral equation by means
of the Nystroem method based on Gauss-Legendre quadrature
and using the power method for deriving the largest in magnitude
eigenvalue and the related left eigenfunction.
Returns a single value which resembles the steady-state ARL.
Sven Knoth
R. B. Crosier (1986), A new two-sided cumulative quality control scheme, Technometrics 28, 187-194.
S. V. Crowder (1987), A simple method for studying run-length distributions of exponentially weighted moving average charts, Technometrics 29, 401-407.
J. M. Lucas and M. S. Saccucci (1990), Exponentially weighted moving average control schemes: Properties and enhancements, Technometrics 32, 1-12.
xtewma.arl
for zero-state ARL computation and
xewma.ad
for the steady-state ARL for normal data.
## will follow
## will follow
Computation of the (zero-state) Average Run Length (ARL) for different types of EWMA control charts monitoring the mean of t distributed data.
xtewma.arl(l,c,df,mu,zr=0,hs=0,sided="two",limits="fix",mode="tan",q=1,r=40)
xtewma.arl(l,c,df,mu,zr=0,hs=0,sided="two",limits="fix",mode="tan",q=1,r=40)
l |
smoothing parameter lambda of the EWMA control chart. |
c |
critical value (similar to alarm limit) of the EWMA control chart. |
df |
degrees of freedom – parameter of the t distribution. |
mu |
true mean. |
zr |
reflection border for the one-sided chart. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided EWMA control chart
by choosing |
limits |
distinguishes between different control limits behavior. |
mode |
Controls the type of variables substitution that might improve the numerical performance. Currently,
|
q |
change point position. For |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
In case of the EWMA chart with fixed control limits,
xtewma.arl
determines the Average Run Length (ARL) by numerically
solving the related ARL integral equation by means of the Nystroem method
based on Gauss-Legendre quadrature.
If limits
is "vacl"
, then the method presented in Knoth (2003) is utilized.
Other values (normal case) for limits
are not yet supported.
Except for the fixed limits EWMA charts it returns a single value which resembles the ARL.
For fixed limits charts, it returns a vector of length q
which resembles the ARL and the
sequence of conditional expected delays for q
=1 and q
>1, respectively.
Sven Knoth
K.-H. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, Appl. Statist. 35, 151-158.
S. V. Crowder (1987), A simple method for studying run-length distributions of exponentially weighted moving average charts, Technometrics 29, 401-407.
J. M. Lucas and M. S. Saccucci (1990), Exponentially weighted moving average control schemes: Properties and enhancements, Technometrics 32, 1-12.
C. M. Borror, D. C. Montgomery, and G. C. Runger (1999), Robustness of the EWMA control chart to non-normality , Journal of Quality Technology 31, 309-316.
S. Knoth (2003), EWMA schemes with non-homogeneous transition kernels, Sequential Analysis 22, 241-255.
S. Knoth (2004), Fast initial response features for EWMA Control Charts, Statistical Papers 46, 47-64.
xewma.arl
for zero-state ARL computation of EWMA control charts in the normal case.
## Borror/Montgomery/Runger (1999), Table 3 lambda <- 0.1 cE <- 2.703 df <- c(4, 6, 8, 10, 15, 20, 30, 40, 50) L0 <- rep(NA, length(df)) for ( i in 1:length(df) ) { L0[i] <- round(xtewma.arl(lambda, cE*sqrt(df[i]/(df[i]-2)), df[i], 0), digits=0) } data.frame(df, L0)
## Borror/Montgomery/Runger (1999), Table 3 lambda <- 0.1 cE <- 2.703 df <- c(4, 6, 8, 10, 15, 20, 30, 40, 50) L0 <- rep(NA, length(df)) for ( i in 1:length(df) ) { L0[i] <- round(xtewma.arl(lambda, cE*sqrt(df[i]/(df[i]-2)), df[i], 0), digits=0) } data.frame(df, L0)
Computation of quantiles of the Run Length (RL) for EWMA control charts monitoring normal mean.
xtewma.q(l, c, df, mu, alpha, zr=0, hs=0, sided="two", limits="fix", mode="tan", q=1, r=40) xtewma.q.crit(l, L0, df, mu, alpha, zr=0, hs=0, sided="two", limits="fix", mode="tan", r=40, c.error=1e-12, a.error=1e-9, OUTPUT=FALSE)
xtewma.q(l, c, df, mu, alpha, zr=0, hs=0, sided="two", limits="fix", mode="tan", q=1, r=40) xtewma.q.crit(l, L0, df, mu, alpha, zr=0, hs=0, sided="two", limits="fix", mode="tan", r=40, c.error=1e-12, a.error=1e-9, OUTPUT=FALSE)
l |
smoothing parameter lambda of the EWMA control chart. |
c |
critical value (similar to alarm limit) of the EWMA control chart. |
df |
degrees of freedom – parameter of the t distribution. |
mu |
true mean. |
alpha |
quantile level. |
zr |
reflection border for the one-sided chart. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided EWMA control chart
by choosing |
limits |
distinguishes between different control limits behavior. |
mode |
Controls the type of variables substitution that might improve the numerical performance. Currently,
|
q |
change point position. For |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
L0 |
in-control quantile value. |
c.error |
error bound for two succeeding values of the critical value during applying the secant rule. |
a.error |
error bound for the quantile level |
OUTPUT |
activate or deactivate additional output. |
Instead of the popular ARL (Average Run Length) quantiles of the EWMA
stopping time (Run Length) are determined. The algorithm is based on
Waldmann's survival function iteration procedure.
If limits
is "vacl"
, then the method presented in Knoth (2003) is utilized.
For details see Knoth (2004).
Returns a single value which resembles the RL quantile of order q
.
Sven Knoth
F. F. Gan (1993), An optimal design of EWMA control charts based on the median run length, J. Stat. Comput. Simulation 45, 169-184.
S. Knoth (2003), EWMA schemes with non-homogeneous transition kernels, Sequential Analysis 22, 241-255.
S. Knoth (2004), Fast initial response features for EWMA Control Charts, Statistical Papers 46, 47-64.
K.-H. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, Appl. Statist. 35, 151-158.
xewma.q
for RL quantile computation of EWMA control charts in the normal case.
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Computation of the survival function of the Run Length (RL) for EWMA control charts monitoring normal mean.
xtewma.sf(l, c, df, mu, n, zr=0, hs=0, sided="two", limits="fix", mode="tan", q=1, r=40)
xtewma.sf(l, c, df, mu, n, zr=0, hs=0, sided="two", limits="fix", mode="tan", q=1, r=40)
l |
smoothing parameter lambda of the EWMA control chart. |
c |
critical value (similar to alarm limit) of the EWMA control chart. |
df |
degrees of freedom – parameter of the t distribution. |
mu |
true mean. |
n |
calculate sf up to value |
zr |
reflection border for the one-sided chart. |
hs |
so-called headstart (enables fast initial response). |
sided |
distinguishes between one- and two-sided EWMA control chart
by choosing |
limits |
distinguishes between different conrol limits behavior. |
mode |
Controls the type of variables substitution that might improve the numerical performance. Currently,
|
q |
change point position. For |
r |
number of quadrature nodes, dimension of the resulting linear
equation system is equal to |
The survival function P(L>n) and derived from it also the cdf P(L<=n) and the pmf P(L=n) illustrate the distribution of the EWMA run length. For large n the geometric tail could be exploited. That is, with reasonable large n the complete distribution is characterized. The algorithm is based on Waldmann's survival function iteration procedure. For varying limits and for change points after 1 the algorithm from Knoth (2004) is applied. For details see Knoth (2004).
Returns a vector which resembles the survival function up to a certain point.
Sven Knoth
F. F. Gan (1993), An optimal design of EWMA control charts based on the median run length, J. Stat. Comput. Simulation 45, 169-184.
S. Knoth (2003), EWMA schemes with non-homogeneous transition kernels, Sequential Analysis 22, 241-255.
S. Knoth (2004), Fast initial response features for EWMA Control Charts, Statistical Papers 46, 47-64.
K.-H. Waldmann (1986), Bounds for the distribution of the run length of geometric moving average charts, Appl. Statist. 35, 151-158.
xewma.sf
for survival function computation of EWMA control charts in the normal case.
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Computation of the (zero-state) Average Run Length (ARL) for modified Shewhart charts deployed to the original AR(1) data where the residuals follow a Student t distribution.
xtshewhart.ar1.arl(alpha, cS, df, delta=0, N1=50, N2=30, N3=2*N2, INFI=10, mode="tan")
xtshewhart.ar1.arl(alpha, cS, df, delta=0, N1=50, N2=30, N3=2*N2, INFI=10, mode="tan")
alpha |
lag 1 correlation of the data. |
cS |
critical value (alias to alarm limit) of the Shewhart control chart. |
df |
degrees of freedom – parameter of the t distribution. |
delta |
potential shift in the data (in-control mean is zero. |
N1 |
number of quadrature nodes for solving the ARL integral equation, dimension of the resulting linear equation system is |
N2 |
second number of quadrature nodes for combining the probability density function of the first observation following the margin distribution and the solution of the ARL integral equation. |
N3 |
third number of quadrature nodes for solving the left eigenfunction integral equation to determine the margin density (see Andel/Hrach, 2000),
dimension of the resulting linear equation system is |
INFI |
substitute of |
mode |
Controls the type of variables substitution that might improve the numerical performance. Currently, |
Following the idea of Schmid (1995), 1-alpha
times the data turns out to be an
EWMA smoothing of the underlying AR(1) residuals. Hence, by combining the solution of
the EWMA ARL integral equation and the stationary distribution of the AR(1) data
(here Student t distribution is assumed) one gets easily the overall ARL.
It returns a single value resembling the zero-state ARL of a modified Shewhart chart.
Sven Knoth
J. Andel, K. Hrach (2000). On calculation of stationary density of autoregressive processes. Kybernetika, Institute of Information Theory and Automation AS CR 36(3), 311-319.
H. Kramer, W. Schmid (2000). The influence of parameter estimation on the ARL of Shewhart type charts for time series. Statistical Papers 41(2), 173-196.
W. Schmid (1995). On the run length of a Shewhart chart for correlated data. Statistical Papers 36(1), 111-130.
xtewma.arl
for zero-state ARL computation of EWMA control charts in case of Student t distributed data.
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