IRCHART Statement: SHEWHART Procedure

You can read individual measurements from a DATA= data set specified in the PROC SHEWHART statement. Each process specified in the IRCHART statement must be a SAS variable in the data set. This variable provides measurements of items indexed by the subgroup-variable. The subgroup-variable, which is specified in the IRCHART statement, must also be a SAS variable in the data set. Each observation in a DATA= data set must contain a measurement for each process and a value for the subgroup-variable. Other variables that can be read from a DATA= data set include

By default, the SHEWHART procedure reads all of the observations in a DATA= data set. However, if the DATA= data set includes the variable _PHASE_, you can read selected groups of observations (referred to as phases) by specifying the READPHASES= option in the IRCHART statement (for an example, see Displaying Stratification in Phases.

For an example of a DATA= data set, see Creating Individual Measurements and Moving Range Charts.

You can read preestablished control limits (or parameters from which the control limits can be calculated) from a LIMITS= data set specified in the PROC SHEWHART statement. For example, the following statements read control limit information from the data set Conlims:[58]

proc shewhart data=info limits=Conlims;
   irchart Weight*ID;
run;

The LIMITS= data set can be an OUTLIMITS= data set that was created in a previous run of the SHEWHART procedure. Such data sets always contain the variables required for a LIMITS= data set; see Table 17.20. The LIMITS= data set can also be created directly using a DATA step.

When you create a LIMITS= data set, you must provide one of the following:

In addition, note the following:

For an example, see Reading Preestablished Control Limits.

You can read individual measurements and moving ranges from a HISTORY= data set specified in the PROC SHEWHART statement. This enables you to reuse OUTHISTORY= data sets that have been created in previous runs of the SHEWHART procedure.

A HISTORY= data set used with the IRCHART statement must contain the following:

The name of the individual measurements variable must be the process specified in the IRCHART statement. The name of the moving range variable must be the prefix process concatenated with the special suffix character R. For example, consider the following statements:

proc shewhart history=Summary;
   irchart (Weight Yieldstrength) * ID;
run;

The data set Summary must include the variables ID, Weight, WeightR, YieldstrengthN, and YieldstrengthR.

Note that if you specify a process name that contains 32 characters, the name of the moving range variable must be formed from the first 16 characters and the last 15 characters of the process name, suffixed with R.

Other variables that can be read from a HISTORY= data set include

By default, the SHEWHART procedure reads all of the observations in a HISTORY= data set. However, if the 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 Reading Individual Measurements and Moving Ranges.

You can read individual measurements, moving ranges, and control limits from a TABLE= data set specified in the PROC SHEWHART statement. This enables you to reuse an OUTTABLE= data set created in a previous run of the SHEWHART procedure. Because the SHEWHART procedure simply displays the information in a TABLE= data set, you can use TABLE= data sets to create specialized control charts. Examples are provided in Specialized Control Charts: SHEWHART Procedure.

The following table lists the variables required in a TABLE= data set used with the IRCHART statement:

Other variables that can be read from a TABLE= data set include

For an example of a TABLE= data set, see Saving Control Limits.