In addition, you can optionally specify one of each of the following statements:
The BY statement specifies variables in the input data set that are used for BY processing. A separate control chart is created for each group of observations defined by the levels of the BY variables. The input data set must be sorted in order of the BY variables.
The ID statement specifies variables used to identify observations. The ID variables must be variables in the DATA= or HISTORY= input data sets.
The ID variables are used in the following ways:
If you create an OUTHISTORY= or OUTTABLE= data set, the ID variables are included. If the input data set is a DATA= data set, only the values of the ID variables from the first observation in each subgroup are passed to the output data set.
If you specify the TABLEID or TABLEALL options in a chart statement, the table produced is augmented by a column for each of the ID variables. Only the values of the ID variables from the first observation in each subgroup are tabulated. See the entry for the TABLEID option in Dictionary of Options: SHEWHART Procedure.
If you specify the BOXSTYLE=SCHEMATICID option or the BOXSTYLE= SCHEMATICIDFAR option in the BOXCHART statement, the value of the first variable listed in the ID statement is used to label each extreme observation. See Output 15.2.3 and Output 15.2.4.