Subsetting observations
Example: Create a subset of the SURVEY12 data set that is only the males.
Recall that the original data set looks like this:

SUBJ    GENDER    HEIGHT    WEIGHT    YEAR

  1       M         68        155      91
  7       F         72        205      90
  9       M         66        120      93
  5       F         63        102      92
  8       M         70        250      91

In the data step, the statement that conditionally includes observations in an output data file is the subsetting IF statement. For instance:

Data Males;
     Set library.Survey12;
     IF Gender='M';
Proc Print;
     ID Subj;
     Title 'Like Example 1 in C&P Chapter 3';
run;      

The Proc Print output indicates this worked fine:

Like Example 1 in C&P Chapter 3

SUBJ    GENDER    HEIGHT    WEIGHT    YEAR

  1       M          68       155      91
  9       M          66       120      93
  8       M         250        70      91

Note that the subsetting IF statement is a special form of the IF statement that does not use THEN.

Subsetting IF statement (data step only) IF expression;

The subsetting IF statement acts like a gate. In the normal flow of execution, each SAS statement in the data step is executed in turn. When the subsetting IF statement is encountered, expression is evaluated. One of two things occur:

• If expression is false-that is, if it has a value of zero (0) or missing (.)-execution of this iteration of the data step stops. Since execution stopped, the end of the data step is not reached. Since the end of the data step is not reached, output to disk does not occur.
• If expression is true-that is, it has any other value other than zero or missing- execution of this iteration of the data step continues.