BY Statement
- BY variables ;
You can specify a BY statement with PROC TTEST to obtain
separate analyses on observations in groups defined by the
BY variables. When a BY statement appears, the procedure
expects the input data set to be sorted in order of the BY
variables.
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 TTEST 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
(in base SAS software).
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 SAS Procedures Guide.
Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.
