Variable Specification (SPCHART command)

The variable specification for I or IR subcommand is

VAR [BY VAR]

You must specify the process variable that contains the value for each individual observation. Each observation is plotted for the individuals chart. The range of n consecutive observations (where n is the value that is specified on the SPAN subcommand) is calculated and plotted for the moving range chart. The range data for the first n-1 cases are missing, but the mean and the limit series are not missing.

Keyword BY and the category variable are optional. When specified, the category variable is used for labeling the category axis and can be any type of variable. If omitted, the category axis is labeled 1 to the number of individual observations in the process variable.

Example

SPCHART /TEMPLATE='ctrl.sgt'
  /IR=SUBSIZE.

• This command requests an individuals chart and a moving range chart.
• The default span (2) and sigma value (3) are used.