Date:         Thu, 13 Apr 2000 00:53:46 GMT
Reply-To:     "Daniel J. Nordlund" <dnordlund@AOL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "Daniel J. Nordlund" <dnordlund@AOL.COM>
Organization: AOL http://www.aol.com
Subject:      Re: help on basic sas programming

N Yiannakoulias <nwy@gpu.srv.ualberta.ca> wrote:

>Hello,
>
>Every time I run into a difficult programming task I
>usually abandon SAS in favour of a language that
>I am more familiar.  In the long run however,
>I think this is costing me in overall efficiency.
>One programming element in SAS continues to confuse me:
>
>Here's are two sample data sets:
>
>id     date            v1      v2
>1      19970401        1       0
>2      19960326        0       1
>...
>
>id2    date2
>1      19960211
>1      19980611
>2      19970912
>2      19961201
>...
>
>My goal (in pseudo code)
>for each id in table 1
>{
>       if id1 equals id2
>       {
>               if (date1 < date2)
>               {
>                       write record to new file
>               }
>       }
>}
>
>In most languages I can simply compare elements in
>arrays and this is as easy as pie to program.  I can't figure
>out how to do it in SAS.  Part of the problem is that I never
>bought a book.  Can anyone help me understand how to do this?
>
>N
>

How about something like the following.  It assumes that the IDs are in sorted
order.   If not, then sort the datasets first.


data one;
  informat date yymmdd8.;
  input id date v1 v2;
cards;
1 19970401 1 0
2 19960326 0 1
;
run;
data two;
  informat date2 yymmdd8.;
  input id2 date2;
cards;
1 19960211
1 19980611
2 19970912
2 19961201
;
run;
data three;
  merge one two(rename=(id2=id));
  by id;
  if date<date2;
run;
proc print data=three;
run;

Hope this helps,

Dan Nordlund