SAS Certification Prep Guide: Base Programming for SAS 9, Third Edition

Using BY-Group Processing

Finding the First and Last Observations in a Group

Creating List Reports explained how to use a BY statement in PROC SORT to sort observations and in PROC PRINT to group observations for subtotals. You can also use the BY statement in the DATA step to group observations for processing.

data temp; 
   set salary; 
   by dept; 
run;

When you use the BY statement with the SET statement,

• the data sets that are listed in the SET statement must be sorted by the values of the BY variable(s), or they must have an appropriate index.
• the DATA step creates two temporary variables for each BY variable. One is named FIRST.variable, where variable is the name of the BY variable, and the other is named LAST.variable. Their ...