Bob, There are only three ways the value of VALID can get set to blank 1) explicit assignment 2) set to missing by the system at the beginning of a BY-group in reading multiple SAS data sets. 3) clobbered by input from SAS or external data Your step rules out 1 and 2. > data check; > set test; > by id measure; > > retain valid; > > if first.id then valid=.; > > if measure=2 then valid=1; > run; VALID must be a variable in TEST. The fact that the print shows blank leads me to think VALID is defined as character in TEST unless the option MISSING is set to blank. Since I cannot verify what you have, but you can, I suggest that you take a look at TEST. If VALID is not there, then make the data set TEST from cards and show your log. Ian_Whitlock@comcast.net ================================= Date: Fri, 24 Sep 2004 16:36:40 -0700 Reply-To: Bob Lan <baoxian_lan@EXCITE.COM> Sender: "SAS(r) Discussion" From: Bob Lan <baoxian_lan@EXCITE.COM> Organization: http://groups.google.com Subject: Retain not retain Content-Type: text/plain; charset=ISO-8859-1 Dear all, Can anyone tell me what happened here? Here is the code: proc sort data=test; by id measure; run; data check; set test; by id measure; retain valid; if first.id then valid=.; if measure=2 then valid=1; run; title; proc print data=check; var id measure valid; run;

Here is the result I have never seen before and don't know what happened: Obs id measure valid 1 100000 2 1 2 100000 4 1 3 100000 5 1 4 100100 2 1 5 100100 4 1 6 100100 5 1 7 100800 2 1 8 100800 4 9 100800 5 10 102100 2 1 11 102100 4 1 12 102100 5 1 13 102400 2 1 14 102400 4 15 102900 2 1 16 102900 4 17 102900 5