topic many-to-one data reshaping and call missing in New SAS User

many-to-one data reshaping and call missing

anming — Sat, 28 Nov 2020 17:51:17 GMT

data one;
input S_id S_i score;
cards;
1 1 98
1 2 76
1 3 63
2 1 96
2 2 85
2 3 76
;
run;

data score_one;
set one;
by S_id S_i;
array ascore(3);
retain ascore1-ascore3;
/*if first.S_id then call missing(of ascore1-ascore3);*/
ascore(S_i)=score;
/*output;*/
if last.S_id then output;
keep S_id ascore1-ascore3;
run;

when I work on the reshaping through by statement, it seems the first.s_id does not take an effect when combining with the call missing routine. As shown above, 
when I comments if first.S_id call missing line, the codes can generate the same data set. Call missing should assign empty values for first-id =1, but we do have 
the values for the first line. I use "output" to display the loop. It is a bit confusing about the data assignment. What is the proper understanding?

Re: many-to-one data reshaping and call missing

Kurt_Bremser — Sat, 28 Nov 2020 18:32:27 GMT

Since your data causes all elements of the array to be filled in every s_id group, the call missing will not have a noticeable effect. If one of your groups missed one of the values 1,2,3 for s_i, the call missing would be necessary.

Re: many-to-one data reshaping and call missing

Astounding — Sat, 28 Nov 2020 22:27:07 GMT

WIth a slight modification to your program, you can observe the effect of CALL MISSING:

data score_one before_the_last;
set one;
by S_id S_i;
array ascore(3);
retain ascore1-ascore3;
if first.S_id then call missing(of ascore1-ascore3);
ascore(S_i)=score;
output before_the_last;
if last.S_id then output score_one;
keep S_id ascore1-ascore3;
run;

Re: many-to-one data reshaping and call missing

anming — Sat, 28 Nov 2020 22:57:24 GMT

this is really cool!