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EWMACHART Statement |
Other variables that can be read from a DATA= data set include
By default, the MACONTROL procedure reads all the observations in a DATA= data set. However, if the data set includes the variable _PHASE_, you can read selected groups of observations (referred to as phases) with the READPHASES= option (for an example, see "Displaying Stratification in Phases" ).
For an example of a DATA= data set, see "Creating EWMA Charts from Raw Data" .
proc macontrol data=parts limits=parms; ewmachart gap*day; run;
The LIMITS= data set can be an OUTLIMITS= data set that was created in a previous run of the MACONTROL procedure. Such data sets always contain the variables required for a LIMITS= data set; see "OUTLIMITS= Data Set" . The LIMITS= data set can also be created directly using a DATA step.
When you create a LIMITS= data set, you must provide the variable _WEIGHT_, which specifies the weight parameter used to compute the EWMAs. In addition, note the following:
Some advantages of working with a LIMITS= data set are that
For an example, see "Reading Preestablished Control Limit Parameters" .
A HISTORY= data set used with the EWMACHART statement must contain the following:
The names of the subgroup mean, subgroup standard deviation, and subgroup sample size variables must be the process name concatenated with the suffix characters X, S, and N, respectively.
For example, consider the following statements:
proc macontrol history=cliphist; ewmachart (gap diameter)*day / weight=0.2; run;
The data set CLIPHIST must include the variables DAY, GAPX, GAPS, GAPN, DIAMTERX, DIAMTERS, and DIAMTERN.
Although a subgroup EWMA variable (named by the process name suffixed with E) is saved in an OUTHISTORY= data set, it is not required in a HISTORY= data set, because the subgroup mean variable is sufficient to compute the EWMAs.
Note that, if you specify a process name that contains eight characters, the names of the summary variables must be formed from the first four characters and the last three characters of the process name, suffixed with the appropriate character.
Other variables that can be read from a HISTORY= data set include
By default, the MACONTROL procedure reads all the observations in a HISTORY= data set. However, if the HISTORY= data set includes the variable _PHASE_, you can read selected groups of observations (referred to as phases) by specifying the READPHASES= option (see "Displaying Stratification in Phases" for an example).
For an example of a HISTORY= data set, see "Creating EWMA Charts from Subgroup Summary Data" .
The following table lists the variables required in a TABLE= data set used with the EWMACHART statement:
Variable | Description |
_EWMA_ | exponentially weighted moving average |
_LCLE_ | lower control limit for EWMA |
_LIMITN_ | nominal sample size associated with the control limits |
_MEAN_ | process mean |
subgroup-variable | values of the subgroup-variable |
_SUBN_ | subgroup sample size |
_SUBS_ | subgroup standard deviation |
_SUBX_ | subgroup mean |
_UCLE_ | upper control limit for EWMA |
_WEIGHT_ | weight (r) assigned to most recent subgroup mean in computation of EWMA |
Other variables that can be read from a TABLE= data set include
For an example of a TABLE= data set, see "Saving Control Limit Parameters" .
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