SAS - Invalid numeric data while searching through an Array - arrays

Question

I am trying to create an array of strings and want to insert a value in it, if it does not exist already in the array.
I read somewhere that we can use 'IN' operator with Array. So, coded it as follows:
DATA WANT;
SET HAVE;
BY ID;
ARRAY R_PROS_SCRN_ID {2} $4. R_PROS_SCRN_ID_1 - R_PROS_SCRN_ID_2;
RETAIN R_PROS_SCRN_ID_1 - R_PROS_SCRN_ID_2;
IF NOT PROS_SCRN_ID IN R_PROS_SCRN_ID THEN DO;
DO I=1 to 2 ;
IF MISSING( R_PROS_SCRN_ID{i}) THEN DO;
R_PROS_SCRN_ID{i} = PROS_SCRN_ID;
LEAVE;
END;
END;
END;
IF LAST.ID THEN OUTPUT;
RUN;
In Array R_PROS_SCRN_ID, I want only the unique values from field PROS_SCRN_ID.
It is throwing error:
NOTE: Invalid numeric data, PROS_SCRN_ID='MED' , at line 17352 column 201.
I think it is because I did not initialize the Array before comparing and hence it is considering it as Numeric Array. But, I have specified the format as $4. Why is it throwing error?
Also, I am not sure if this is the best way get unique values in an Array. Is there any better way to implement this?

Answer 1

Your code appears to be collecting unique values by group, pivoting from a tall data structure to a wide data structure.
One of the clearest DATA step ways is to use what we call DOW loop in which SET is within the loop. This sample code presumes no more than 10 unique satellite values per group. (The by variables can be thought of as key variables, and all other variables would be satellites)
data have;
input user_id screen_id ;
datalines;
1 1
1 2
1 1
1 1
1 1
1 3
2 1
2 1
2 1
3 0
4 1
4 2
4 3
5 11
5 11
5 11
5 5
5 1
5 5
5 6
5 1
run;
data want;
_index = 0;
do until (last.user_id);
set have;
by user_id;
array ids screen_id1-screen_id10;
if screen_id not in ids then do;
_index + 1;
ids(_index) = screen_id;
end;
end;
drop _index screen_id;
run;
One of the clearest procedural ways is to select the unique values and transpose them.
proc sql;
create view uniqueScreenByUser as
select distinct user_id, screen_id
from have
order by user_id
;
proc transpose data=uniqueScreenByUser prefix=screen_id out=wantWide(drop=_name_);
by user_id;
var screen_id;
run;