Date:         Thu, 17 Mar 2011 17:43:56 -0400
Reply-To:     Sophia Tong <sophiDT@HOTMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Sophia Tong <sophiDT@HOTMAIL.COM>
Subject:      Fill in missing values

Dear listers,

I have a large data with multiple observations per subject, however, the
subject id only entered once. so the data look like this:
                                 Obs    id     area

                                  1    UC013     116653
                                  2    .         73231
                                  3    .         206861
                                  4    .         104948


                                 28    .         118836
                                 29    UC014     76621
                                 30    UC015     118369
                                 31    .         83335
                                 32    .         94987
                                 33    .         368088
                                 34    .         245277
                                 35    .         59533
                                 36    UC017     152012
                                 37    .         89020
                                 38    .         233892
                                 39    .         234393
 How can I fill in those missing IDs?
  Thanks,
Sophia