topic Re: Passing a vector of strings as an argument to an IML function in SAS/IML Software and Matrix Computations

Passing a vector of strings as an argument to an IML function

Dima — Wed, 19 Sep 2012 11:47:17 GMT

Hello,

I have defined an IML function which takes 2 arguments : one as numeric, the other as character.

proc iml;

     age_vect=J(10,1,10);
     text_vect=J(10,1,"YES");

     start test(age,text);
          if text="NO" then
               temp=age+0;
          else if text="YES" then
               temp=age+10;
          return(temp);
     finish test;

Result_1=test(10,"YES");

Result_2=apply("test",age_vect,text_vect);

quit;

I want to apply this function to vectors, but it doesn't work (Result_2).

But this function will work if i try to calculate Result_1.

Is it impossible to pass vectors of characters to IML function?

Re: Passing a vector of strings as an argument to an IML function

IanWakeling — Thu, 20 Sep 2012 08:24:35 GMT

I think the answer may be that the APPLY function is not designed to work with modules that take text arguments, however it doesn't always make this clear. For example the following code runs without error but returns a text matrix with a single element.

start uc(t);
return(upcase(t));
finish;

cin={"a","b","c"};
cout=apply("uc",cin);
print cout;

Have a look at the CHOOSE function as it can be used to get what you want without writing a module. For example:

Result_2=choose(text_vect="YES", age_vect+10, age_vect);

Re: Passing a vector of strings as an argument to an IML function

IanWakeling — Thu, 20 Sep 2012 10:07:48 GMT

I did a little more investigation, my code above does return a 3x1 text matrix, but the second and third elements are blank. (Rick can you investigate this please?).

Re: Passing a vector of strings as an argument to an IML function

Dima — Thu, 20 Sep 2012 11:36:07 GMT

Thank you for your suggestion about the CHOOSE function that I didn't know before. It could be helpful but not in my case.

The code above is not what I really want to do, my function is much more complex so I can't find an equivalent using CHOOSE function.

For the moment, I make my function work by coding as numbers the different strings I want to pass to my function. But that way, the code is less understandable.

Re: Passing a vector of strings as an argument to an IML function

IanWakeling — Thu, 20 Sep 2012 12:24:45 GMT

The APPLY function is really nothing more than an implied loop over all the elements of a matrix, so instead of your suggested approach, you could write an explicit loop over each element. Along the lines of:

new_age=age_vect;

do i=1 to nrow(text_vect);

if text_vect="YES" then new_age=new_age+10;

end;

Re: Passing a vector of strings as an argument to an IML function

Rick_SAS — Thu, 20 Sep 2012 12:52:19 GMT

I agree that there seems to be a problem with calling APPLY with character arguments.

There's no need to recode anything: just use a loop to call the scalar function that you've already written. It's not as general, but it should work adequately.

start MyApply(age_array,text_array);
   temp = J(nrow(age_array),1);
   do i = 1 to nrow(age_array);
      age = age_array;
      text = strip(text_array);

      temp = test(age, text);
   end;
   return(temp);
finish;

age_vect = {1,2,3,4,5};
text_vect = {YES, NO, NO, NO, YES};
r = MyApply(age_vect, text_vect);
print r;