R: Online monitoring

onlinem {dvqcc}

R Documentation

Online monitoring

Description

Online T2.var and W.var control charts for monitoring batch processes based on VAR model. This approach is fully described in "Marcondes Filho, D., & Valk, M. (2020). Dynamic VAR Model-Based Control Charts for Batch Process Monitoring. European Journal of Operational Research."

Usage

onlinem(
  data,
  size,
  newdata,
  Lc = 50,
  Lr = 30,
  confidence.level = 0.99,
  type = "T2.var",
  covvar = "empirical",
  plot = TRUE,
  var.estimates = FALSE
)

Arguments

`data`	dataframe of reference dataset. For each batch, variables are arranged in lines and columns are time-instants. The different batches are combined in a single dataset through rbind
`size`	number of variables
`newdata`	dataframe of one or more new batches for monitoring (each with same number of variables and time instants of `data`). Different batches are combined in a single dataset through rbind
`Lc`	length of the coupled vector
`Lr`	length of random vector (Lr<Lc)
`confidence.level`	H0 probability to be consider to define the quantile (default is 0.99)
`type`	"T2.var" for Hotelling chart (default) and "W.var" for Generalized Variance chart
`covvar`	"empirical" for sample covariance of coefficients (default) and "theoretical" for estimated theoretical covariance
`plot`	TRUE shows the charts plots (default TRUE)
`var.estimates`	TRUE show informations about the VAR modeling phase and the elements for setting T2.var / W.var control charts (default FALSE)

Details

The maximum number of variables is five.

All batches must have the same number of time-instants.

This method is based on the use of "coupled vectors (cv)" (for more details, see Marcondes Filho, D., & Valk, M., 2020").

The parameters Lc and Lr define the cv structure.

Considering the new ongoing batch under monitoring:

Lc is the number of elements of cv. (Lc is smaller than the number of time-instants); Lr is the number of elements in cv randomly chosen from the in control batches in the reference dataset; Lc-Lr is the number of elements in cv from the last (Lc-Lr) observations of the new ongoing batch.

Default is Lc= 50 e Lr=30.

The batches in dataset "data" are considered to be in control

Value

beyond.limits: returns the time-instants of each batch that the T2.var (or W.var) score are above the control limit

arl: returns for each new batch the mean number of time-instants before a signal is given by the control chart (arl=n/g, where n is the overall number of time-instants and g is the number of time-instants above the control limit)

time.to.first.detection (TFD): returns for each new batch the first time-instant (the most recently instant) that can be considered as a possible signal of process change. TFD is the first point (t*) above the limit followed by two consecutive points above the control limit

artl: returns the cumulative rate of the overall time-instants (n) until the first three consecutive points are above the control limit. The artl is computed using the first of these three points, that is, artl=t*/n

varest: If var.estimates=TRUE, it returns the Lim_T2 vector (or Lim_W vector) of the T2.var (or W.var) control limits to each time-instant; the T2.var (or W.var) scores for each new batch to each time-instant [(tnew) matrix for the T2.var and (wnew) matrix for the W.var scores]; the number (I) of reference batches; the number (C=size*size) of estimated phis coefficients; the number (Inew) of new batches; the number (n) of time-instants and the (cov) list including the estimated mean covariance from the reference batches to each time-instant

#' @examples

# Example 1: Monitoring considering two variables and Inew=5 in control batches

mydata=simon()

T2.var.on=onlinem(data=mydata$data,size=2,newdata=mydata$newdata) W.var.on=onlinem(data=mydata$data,size=2,type="W.var",newdata=mydata$newdata)

# Example 2: Monitoring considering two variables and Inew=10 in control batches

B1=matrix(c(-0.3, 0.4, 0.4, 0.5), 2, byrow=TRUE) B1new=B1 mydata2=simon(n=100,I=200,size=2,Inew=10,n1=50,B1=B1,varcov=diag(2),B1new=B1new) T2.var.on=onlinem(data=mydata2$data,size=2,newdata=mydata2$newdata, plot=F) W.var.on=onlinem(data=mydata2$data,size=2,type="W.var",newdata=mydata2$newdata, plot=F)

# Example 3: Monitoring considering three variables and Inew=10 out of control batches