Question

data tempx1;
  input ID;
  cards;
  1
  2
  3
  4
  ;
run;

data tempx2;
   set tempx1;
   array diag{4} d1 d2 d3 d4 (1,2,3,4);
     do i = 1 to 4;
      if diag[i] = ID then diag[i] = 1; else diag[i] = 0;
     end;
    drop i;
run;

I want 1’s to be in the diagonal of the array, what did i do wrong here?

Answer 1

When you initialise an array with a set of values, the values you give it are only set once. They don’t get re-set for each implicit loop of the dataset.

You therefore must do this explicitly. The following code will work for you:

data tempx2;
set tempx1;
array diag{4} d1 d2 d3 d4 (1,2,3,4);

do i = 1 to 4;
diag[i] = i;
end;

do i = 1 to 4;
if diag[i] = ID then diag[i] = 1; else diag[i] = 0;
end;

drop i;

run;

Here is a demo which should make it easier to understand why this works:

data test;
set tempx1;
array diag{4} d1 d2 d3 d4 (1,2,3,4);
put _all_;
output;
if _n_ = 1 then diag{1} = 10;
if _n_ = 3 then diag{1} =  20;
put _all_;
output;
run;