How do I add a column to a dataset that stores categories from three other columns?

[DoctorShemp]

New SAS user here!

In my dataset I am comparing three different diets (A,B, and C) in how they affect weight loss. Currently, my data has a column for the weightloss, followed by three columns A, B, and C. If A=1 it means the person was on diet A (columns B and C would have 0, the diets are mutually exclusive). I don't want three columns with 1s and 0s like this though. I just want one simple column called "Diet" That stores either A, B, or C. How do I do this?

[Reeza]

You can code them as A, B, C or 1, 2, 3.

name = whichn(1, A, B, C);

I think this would code it as 1, 2, 3. If that works for you.

[r_behata]

data have;
input  a b c ;
cards;
1 0 0
0 1 0
0 0 1
0 1 0
run;

data want;
set have;
array nm a b c;
diet=' ';
do i =1 to dim(nm) while(diet eq ' ') ;
	if nm[i] > 0 then diet=vname(nm[i]);
end;

drop a b c i;
run;

[PGStats · Accepted solution]

Use the transformation

diet = char("ABCX", whichn(1, A, B, C, 1));

[DoctorShemp]

Thank you! this is the simplest solution that did exactly what I was trying to do.

Thank you to everyone else who responded as well, this community is crazy helpful