DROP variable-list ;

The DROP statement specifies that some variables be excluded from the OUT= data set. Only the time series and event variables can be specified in a DROP statement. None of the BY variables or the time ID variable DATE can be excluded from the OUT= data set. If they are referenced in a DROP statement, a warning message is given and the reference is ignored. Use the WHERE statement for selection based on BY variables, and use the RANGE statement for date selections.

The variable list can contain variable names or name range specifications. See Variable Lists for details.

Only one DROP or one KEEP statement can be used. KEEP and DROP are mutually exclusive.

There is a default DROP or KEEP list for each file type. Usually, descriptor type variables, like footnotes, are not included in the default KEEP list. If you specify a DROP statement, the default list becomes undefined.

You can also use the DROP= data set option to control which variables to exclude from the OUT= data set. However, the DROP statement differs from the DROP= data set option in several aspects:

• The DROP statement selection is applied before variables are read from the data file, while the DROP= data set option selection is applied after variables are read and as they are written to the OUT= data set. Therefore, using the DROP statement instead of the DROP= data set option is much more efficient.

• If the DROP statement causes all series variables to be excluded, then no observations are output to the OUT= data set.

• The DROP statement variable specifications are applied to each cross section independently. This behavior may produce variables different from those produced by the DROP= data set option when order-range variable list specifications are used.