SPSS® 12.0 Command Syntax Reference

Overview
DO IF 493
The DO IF—END IF structure conditionally executes one or more transformations on subsets
of cases based on one or more logical expressions. The ELSE command can be used within
the structure to execute one or more transformations when the logical expression on DO IF
is not true. The ELSE IF command within the structure provides further control.
The DO IF—END IF structure is best used for conditionally executing multiple transformation
commands, such as COMPUTE, RECODE, and COUNT. IF is more efficient for
executing a single conditional COMPUTE-like transformation. DO IF—END IF transforms
data for subsets of cases defined by logical expressions. To perform repeated transformations
on the same case, use LOOP—END LOOP.
A DO IF—END IF structure can be used within an input program to define complex files
that cannot be handled by standard file definition facilities. See “Complex File Structures”
on p. 499 for an example.
See END FILE for information on using DO IF—END IF to instruct the program to stop
reading data before it encounters the end of the file or to signal the end of the file when
creating data. See p. 422 for an example of using DO IF—END IF with END FILE to concatenate
raw data files.
Basic Specification
The basic specification is DO IF followed by a logical expression, a transformation command,
and the END IF command, which has no specifications.
Syntax Rules
• The ELSE IF command is optional and can be repeated as many times as needed.
• The ELSE command is optional. It can be used only once and must follow any ELSE IF
commands.
• The END IF command must follow any ELSE IF and ELSE commands.
• A logical expression must be specified on the DO IF and ELSE IF commands. Logical
expressions are not used on the ELSE and END IF commands.
• String values used in expressions must be specified in quotation marks and must include
any leading or trailing blanks. Lowercase letters are distinguished from uppercase letters.
• To create a new string variable within a DO IF—END IF structure, you must first declare
the variable on the STRING command.
• DO IF—END IF structures can be nested to any level permitted by available memory. They
can be nested within LOOP—END LOOP structures, and loop structures can be nested
within DO IF structures.