Step-by-Step Programming with Base SAS 9.4

Working with Grouped Data

Understanding the Basics of Grouping Data

The basic method for grouping data is to use a BY statement:

BY list-of-variables;

The BY statement can be used in a DATA step with a SET, MERGE, MODIFY, or UPDATE statement, or it can be used in SAS procedures.

To work with grouped data using the SET, MERGE, MODIFY, or UPDATE statements, the data must meet these conditions:

• The observations must be in a SAS data set, not an external file.
• The variables that define the groups must appear in the BY statement.
• All observations in the input data set must be in ascending or descending numeric or character order, or grouped in some way, such as by calendar month or by a formatted value, according to the variables ...