Automating creation of an indicator variable in SAS - sas

Question

I am working with a SAS dataset that includes up to 30 medications prescribed to an individual patient. The medications are coded med1, med2 ... med30. Each medication is represented by a 5-digit character variable. Using the identifier, I can then code the name of the drug, and whether that particular medication is a topical antibiotic or a systemic antibiotic.
For each patient, I want to use all 30 medication codes to create one variable indicating whether the patient got a topical antibiotic only, a systemic antibiotic only, or both a topical and an oral antibiotic. So if any of the 30 medications is a systemic antibiotic, I want the patient coded as oral_antibiotic=1.
I currently have this code:
data want;
set have;
array meds[30] med1-med30;
if meds[i] in ('06925' '06920') then do;
penicillin=1;
oral_antibiotic=1;
end;
else if meds[i] in ('03197') then do;
neosporin=1;
topical_antibiotic=1;
end;
.... (many more do loops with many more medications)
run;
The problem is that this code creates one indicator variable instead of 30, overwriting previous information.
I think that I really need 30 indicator variables, indicating whether each of the 30 drugs is an oral or topical antibiotic, before I write code that says if any of the drugs are oral antibiotics, the patient received an oral antibiotic.
I am new to macros and would really appreciate help.
data current;
input med1 med2 med3;
cards;
'06925' '06920' '03197' ;
run;
And I want this:
data want;
input med1 topical_antibiotic1 oral_antibiotic1 med2 topical_antibiotic2 oral_antibiotic2 med3 topical_antibiotic3 oral_antibiotic3;
cards;
'06925' 0 1 '06920' 0 1 '03197' 1 0
;
run;

Answer 1

I think that I really need 30 indicator variables, indicating whether
each of the 30 drugs is an oral or topical antibiotic, before I write
code that says if any of the drugs are oral antibiotics, the patient
received an oral antibiotic.
That's not true. Your current approach is fine as long as you're not resetting them. You don't show us the full code, so it's hard to say, but I'm going to assume that's what is happening here.
Your loop should look like:
array med(30) med1-med30;
*set to 0 at top of the loop;
topical_antibiotic=0; oral_antibiotic=0;
do i=1 to dim(med);
if med(i) in (.....) /*list of topical codes*/ then topical_antibiotic=1;
else if med(i) in (.....) /*list of oral codes*/ then oral_antibiotic=1;
end;
This assumes that an antibiotic cannot be in both Topical/Oral groups. If it can, you need to remove the ELSE from the second IF statement.

Answer 2

I agree that you probably only need one indicator variable for each drug group, (medication of interest). Seems like you just want to know for each subject, "Do they have it?" This example flips the arguments of the IN operator. If you had given more example data I could have done better with this example.
data current;
infile cards missover;
array med[3] $5;
input med[*];
oral_antibotic = '069' in: med; /*Assume oral all start with '069'*/;
topical_antibotic = '03197' in med;
cards;
06925 06920 03197
06925
;;;;
run;