Dummy Coding a Categorical Variable Using a Macro Program

data test;
  input a b;
datalines;
1 3
2 4
3 5
1 3
2 4
3 5
;
run;
%macro recode(myvar, num1, num2);
   array &myvar._a(*) &myvar.&num1 - &myvar.&num2;

   do i = &num1 to &num2;
     &myvar._a(i - &num1 + 1 ) = .;
   end;

  do i = &num1 to &num2;
	  if (&myvar = i) then &myvar._a(i - &num1 + 1 ) = 1;
	  if (&myvar > .) and (&myvar ~= i) then &myvar._a(i - &num1 + 1) = 0;
  end;
%mend;

options mprint mlogic;
data test2;
  set test;
  %recode(a, 1, 3);
  %recode(b, 3, 5);
drop i;
run;
proc print data = test2;
run;

Obs    a    b    a1    a2    a3    b3    b4    b5

 1     1    3     1     0     0     1     0     0
 2     2    4     0     1     0     0     1     0
 3     3    5     0     0     1     0     0     1
 4     1    3     1     0     0     1     0     0
 5     2    4     0     1     0     0     1     0
 6     3    5     0     0     1     0     0     1