BY Statement

The SURVEYREG Procedure

BY Statement

BY variables ;

You can specify a BY statement with PROC SURVEYREG to obtain separate analyses on observations in groups defined by the BY variables.

Note that using a BY statement provides completely separate analyses of the BY groups. It does not provide a statistically valid subpopulation or domain analysis, where the total number of units in the subpopulation is not known with certainty. For more information on subpopulation analysis for sample survey data, refer to Cochran (1977).

When a BY statement appears, the procedure expects the input data sets to be sorted in order of the BY variables. If you specify more than one BY statement, the procedure uses only the latest BY statement and ignores any previous ones.

If your input data set is not sorted in ascending order, use one of the following alternatives:

Sort the data using the SORT procedure with a similar BY statement.
Specify the BY statement option NOTSORTED or DESCENDING in the BY statement for the SURVEYREG procedure. The NOTSORTED option does not mean that the data are unsorted but rather that the data are arranged in groups (according to values of the BY variables) and that these groups are not necessarily in alphabetical or increasing numeric order.
Create an index on the BY variables using the DATASETS procedure.

For more information on the BY statement, refer to the discussion in SAS Language Reference: Concepts. For more information on the DATASETS procedure, refer to the discussion in the SAS Procedures Guide.

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