How can you filter observations in a DATA step?

Filtering observations in a DATA step can be effectively achieved by using the IF statement. The IF statement allows you to specify conditions that determine which observations are processed and which are excluded from the output data set. This means that only observations meeting the defined condition will be included in the resulting data set, providing a flexible and powerful way to manipulate data directly during the DATA step execution.

For instance, if you have a dataset of employee information and you want to extract only those employees from a specific department, you can write an IF statement that checks the department variable. The IF condition will evaluate for each observation, and if it evaluates to true, that observation will be kept in the output dataset.

The concept of using a WHERE clause is valid for filtering data but is typically applied in procedures or SQL processing rather than within the DATA step itself. SELECT statements are generally associated with SQL processing, and implementing a PROC step also shifts the operation away from the DATA step context. Therefore, while there are multiple methods to filter data in SAS, the IF statement stands out as a direct approach tailored for the DATA step environment.