Date:         Tue, 28 Oct 2008 03:07:21 -0700
Reply-To:     Patrick <patrick.matter@GMX.CH>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Patrick <patrick.matter@GMX.CH>
Organization: http://groups.google.com
Subject:      Re: Numbering missing visits
Comments: To: sas-l@uga.edu
Content-Type: text/plain; charset=ISO-8859-1

May be something like that?

data visit;
   input pt:$1 visdat:date. visitid :$1.;
   format visdat date.;
   cards;
1  12JAN2008  1           .
1  20JAN2008  2           .
1  03FEB2008  M           1
1  15FEB2008  M           2
2  03JAN2008  1           .
2  27JAN2008  M           1
2  12FEB2008  2           .
2  25FEB2008  3           .
2  12MAR2008  M           1
2  28MAR2008  M           2
2  19APR2008  M           3
;;;;
   run;
proc sort data=visit;
   by pt visdat;
   run;
data visit;
/*   call missing(count); */
   do until(last.visitID);
      set work.visit;
      by pt visitID notsorted;
      if visitID eq 'M' then count + 1;
      else count=.;
      output;
      end;
   run;
proc print;
   run;