Transposing Data Using PROC SUMMARY'S IDGROUP Option
When clinical data are stored with multiple observations per subject, a common task is to rearrange the data so there is only one observation per subject. That single observation contains all or part of the information previously spread over multiple observations. Such rearranging of data is commonly done with either PROC TRANSPOSE or with a data step that often contains one or more arrays. There is a little used alternative to these methods, the IDGROUP option in PROC SUMMARY. The method is little used since the task is not made explicit in the documentation for the procedure and it has not been described in any papers that the authors could find at SUGI, SAS Global Forum, or various regional user group meetings.