Group Processing Using the BY Statement
Like the CLASS statement, the BY statement specifies variables to
use for categorizing observations.
|
General form, BY statement:
BY variable(s);
where variable(s) specifies
category variables for group processing. |
But
BY and CLASS differ in two key ways:
-
Unlike CLASS processing, BY processing requires that your data already be sorted or indexed in the order of the BY variables. Unless data set observations are already sorted, you will need to run the SORT procedure before using PROC MEANS with any BY group.CAUTION:Be careful when sorting data sets to enable group processing. If you don't specify an output data set by using the OUT= option, PROC SORT will overwrite your initial data ...
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