Date:         Mon, 27 Oct 1997 18:13:18 +0000
Reply-To:     Chris.Murphy@PAREXEL.CO.UK
Sender:       "SAS(r) Discussion" <SAS-L@UGA.CC.UGA.EDU>
From:         Chris Murphy <Chris.Murphy@PAREXEL.CO.UK>
Subject:      Re[2]: Generating trinomial variate?
Content-Type: text/plain; charset=US-ASCII

     All,
 
     It seems that if a conditional 'IF' is carried out on a variable that
     is not common to two datasets that are being merged, then the
     following peculiar action is seen to take place (observe the missing
     'value' where patnum = 2 on the 'test' dataset!!).
 
     However if the dataset 'test' did not contain the conditional loop and
     was then set in a new data step with the conditional do loop applied
     in the new step then then 'value' would not be missing for the
     observation where patnum = 2; it would be 1 as expected.
 
     Can anyboy explain.  I looked at this using v609 on a VAX platfrom.
     I haven't had time to experiment further but I would welcome a
     reasonable explanation.
 
 
 
     *******************code**************************************
 
     data one;
     patnum = 1;
     outv = 'a';
     output;
     patnum = 2;
     outv ='a';
     output;
     patnum = 3;
     outv = 'b';
     output;
     run;
 
     proc sort data = one;
     by outv;
     run;
 
     title1 "dataset one";
     proc print;
     run;
 
     data two;
     outv = 'a';
     value = 1;
     output;
     outv = 'b';
     value = 2;
     output;
     run;
 
     title1 "dataset two";
     proc sort data = two;
     by  outv;
     run;
 
     proc print;
     run;
 
     data test;
     merge one two;
     by outv;
     if patnum = 1 then do;
     outv = ' ';
     value = .;
     end;
     run;
 
     title1 "dataset test";
     proc print;
     run;
 
 
     **********output *******************
 
 
     dataset one
 
     OBS    PATNUM    OUTV
 
     1        1       a
     2        2       a
     3        3       b
 
     dataset two
 
     OBS    OUTV    VALUE
 
     1      a        1
     2      b        2
 
     dataset test
 
     OBS    PATNUM    OUTV    VALUE
 
     1        1                .
     2        2       a        .
     3        3       b        2
 
 
 
     Regards
 
     Chris.