### 13.4 SELECT IF

    SELECT IF expression.

`SELECT IF` selects cases for analysis based on the value of expression. Cases not selected are permanently eliminated from the active dataset, unless `TEMPORARY` is in effect (see TEMPORARY).

Specify a boolean expression (see Expressions). If the value of the expression is true for a particular case, the case will be analyzed. If the expression has a false or missing value, then the case will be deleted from the data stream.

Place `SELECT IF` as early in the command file as possible. Cases that are deleted early can be processed more efficiently in time and space.

When `SELECT IF` is specified following `TEMPORARY` (see TEMPORARY), the `LAG` function may not be used (see LAG).