topic Re: automatically retained in SAS Programming

automatically retained

fbl204653 — Wed, 23 Aug 2017 02:03:26 GMT

Hi SAS experts,

when I ran the following program, I found y was automatically retained for x=4 in data test2. What happed?

Thanks!

data test;
   input x y;
   cards;
   1 .
   3 .
   ;
run;

data test1;
   input x;
   cards;
   3
   4
   ;
run;
data test2;
   set test(in=a)
        test1(in=b);
   if b then do;
       if x=3 then y=4;
   end;
run;

Re: automatically retained

PGStats — Wed, 23 Aug 2017 02:57:14 GMT

There is no y variable in dataset test1 so the value of y isn't reset to missing when test1 is read.

Re: automatically retained

Astounding — Wed, 23 Aug 2017 03:01:16 GMT

Any variable that comes from any SAS data set is automatically retained. Since Y comes from a SAS data set, it is automatically retained.

A small complication: when switching data sets (from TEST to TEST1 in the SET statement), Y is reset to missing. You can see that by adding this statement after the SET statement:

put Y;

But once Y is set to 4, it remains 4 (unless changed by subsequent programming statements). As @PGStats said, reading an observation from TEST1 does not replace Y.

Re: automatically retained

fbl204653 — Wed, 23 Aug 2017 03:08:35 GMT

Thanks!

Re: automatically retained

fbl204653 — Wed, 23 Aug 2017 03:10:07 GMT

Thanks!

Re: automatically retained

PGStats — Wed, 23 Aug 2017 03:23:39 GMT

My answer is not quite right. You should mark @Astounding answer as the correct answer instead.