SAS 9.4 Language Reference, 3rd Edition

Chapter 20

BY-Group Processing in the

DATA Step

Definitions for BY-Group Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427

Syntax for BY-Group Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428

Understanding BY Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429

BY Groups with a Single BY Variable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429

BY Groups with Multiple BY Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429

Invoking BY-Group Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430

Determining Whether the Data Requires Preprocessing for

BY-Group Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431

Preprocessing Input Data for BY-Group Processing . . . . . . . . . . . . . . . . . . . . . . . 431

Sorting Observations for BY-Group Processing . . . . . . . . . . . . . . . . . . . . . . . . . . 431

Indexing for BY-Group Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432

How the DATA Step Identifies BY Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432

Processing Observations in a BY Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432

Using a Name Literal as the BY-Group Variable . . . . . . . . . . . . . . . . . . . . . . . . . . 432

How SAS Determines FIRST.variable and LAST.variable . . . . . . . . . . . . . . . . . . 433

Example 1: Grouping Observations by State, City, ZIP Code, and Street . . . . . . . 433

Example 2: Grouping Observations by City, State, ZIP Code, and Street . . . . . . . 435

Example 3: A Change Affecting FIRST.variable . . . . . . . . . . . . . . . . . . . . . . . . . . 435

Processing BY-Groups in the DATA Step . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436

Processing BY-Groups Conditionally . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437

Data Not in Alphabetic or Numeric Order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438

Data Grouped by Formatted Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439

Example 1: Using GROUPFORMAT with Formats . . . . . . . . . . . . . . . . . . . . . . . 439

Example 2: Using GROUPFORMAT with Formats . . . . . . . . . . . . . . . . . . . . . . . 439

Definitions for BY-Group Processing

BY-group processing

is a method of processing observations from one or more SAS data sets that are

grouped or ordered by values of one or more common variables. The most common

use of BY-group processing in the DATA step is to combine two or more SAS data

sets. To do this, you use the BY statement with a SET, MERGE, MODIFY, or

UPDATE statement.

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