To continue this thread in case somebody faces the same issue (or as a reference to myself who might need it later), I managed to count unique polymorphisms after I transposed them each one in their own column using the following code data PrWant; set hivfull.pr_polymorph; array pr_polymorph{24}pr_polymorph1-pr_polymorph24; array new {24} $20 _temporary_; do _n_=1 to 24; new{_n_}=pr_polymorph{_n_}; end; call sortc(of new{*}); count=(new{1}>''); do _n_=2 to 24; if new{_n_} ne new{_n_-1} then count + 1; end; run; The next step would be to evaluate which polymorphisms are the most common regardless of where they are placed in the column, it is likely that polymorphism A in column 23 could be found in a different column number for another patient, which is why i think it would've been more useful to have each polymorphism as its own column name and then rows would check if it is present or not. ... View more

I sort of managed to take them into their own column using PROC TRANSPOSE. I suppose I could use other procedures that allow me to count each individual polymorphism proc transpose data=long out=ordered prefix=polymorph; by id; var polymorph; run; Eventually I would like to associate all the different PR_polymorphisms under a single category ... View more

I modified the first part of the code because I think you meant to use COUNTW() instead of COUNT()   I have attached a screenshot with some of the results, i was wondering if the idea here was to extract only one value into the polyMorph column according to the value of i. Would it be possible of instead of having one row per polymoprhism, you could have several columns for each polymorphism.    data long; set mydata; id=_n_; n_loop=countw(Pr_poly, ","); do i=1 to n_loop; polyMorph=scan(pr_poly, i, ','); output; end; run; ... View more