Merge and create variable in merged dataset in same step - merge

Question

I am merging two datasets in SAS, "set_x" and "set_y", and would like to create a variable "E" in the resulting merged dataset "matched":
* Create set_x *;
data set_x ;
input merge_key A B ;
datalines;
1 24 25
2 25 25
3 30 32
4 32 32
5 20 32
6 1 1
;
run;
* Create set_y *;
data set_y ;
input merge_key C D ;
datalines;
1 1 1
2 2 1
3 1 1
4 2 1
5 1 1
7 1 1
;
run;
* Merge and create E *;
data matched unmatched_x unmatched_y ;
merge set_x (in=x) set_y (in=y) ;
by merge_key ;
if x=y then output matched;
else if x then output unmatched_x ;
else if y then output unmatched_y ;
IF C = 2 THEN DO ;
E = A ;
END;
ELSE DO ;
E = floor(B - D) ;
END ;
run ;
However, in the resulting table "matched", the values of E are missing. E is correctly calculated if I only output matched values (i.e. using if x=y;).
Is it possible to create "E" in the same data step if outputting unmatched as well as matched observations?

Answer 1

You have output the results before E is computed, then E is set to missing when next iteration starts. So you want E to be available before the output,
data matched unmatched_x unmatched_y ;
merge set_x (in=x) set_y (in=y) ;
by merge_key ;
IF C = 2 THEN DO ;
E = A ;
END;
ELSE DO ;
E = floor(B - D) ;
END ;
if x=y then output matched;
else if x then output unmatched_x ;
else if y then output unmatched_y ;
run ;