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The SHEWHART Procedure


The basic syntax for the MCHART statement is as follows:

MCHART process * subgroup-variable ;

The general form of this syntax is as follows:

MCHART processes * subgroup-variable <(block-variables)> <symbol-variable | 'character'> / <options> ;

You can use any number of MCHART statements in the SHEWHART procedure. The components of the MCHART statement are described as follows.


identify one or more processes to be analyzed. The specification of process depends on the input data set specified in the PROC SHEWHART statement.

A process is required. If you specify more than one process, enclose the list in parentheses. For example, the following statements request distinct median charts for Weight, Length, and Width:

proc shewhart data=Measures;
   mchart (Weight Length Width)*Day;

is the variable that identifies subgroups in the data. The subgroup-variable is required. In the preceding MCHART statement, Day is the subgroup variable. For details, see Subgroup Variables.


are optional variables that group the data into blocks of consecutive subgroups. The blocks are labeled in a legend, and each block-variable provides one level of labels in the legend. See Displaying Stratification in Blocks of Observations for an example.


is an optional variable whose levels (unique values) determine the symbol marker or character used to plot the medians.

  • If you produce a line printer chart, an 'A' is displayed for the points corresponding to the first level of the symbol-variable, a 'B' is displayed for the points corresponding to the second level, and so on.

  • If you produce traditional graphics, distinct symbol markers are displayed for points corresponding to the various levels of the symbol-variable. You can specify the symbol markers with SYMBOL statements. See Displaying Stratification in Levels of a Classification Variable for an example.


specifies a plotting character for line printer charts. For example, the following statements create a median chart using an asterisk (*) to plot the points:

proc shewhart data=Values lineprinter;
   mchart Weight*Day='*';

enhance the appearance of the charts, request additional analyses, save results in data sets, and so on. The section Summary of Options, which follows, lists all options by function. Dictionary of Options describes each option in detail.

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