topic Re: SAS IML IF/THEN/ELSE in SAS/IML Software and Matrix Computations

SAS IML IF/THEN/ELSE

abbaskashif — Wed, 18 Jan 2017 19:07:38 GMT

How can we apply IF/THEN/ELSE statement to each element in a n*m matrix so that the result is also a n*m matrix of TRUE/FALSE?

Re: SAS IML IF/THEN/ELSE

Rick_SAS — Wed, 18 Jan 2017 19:22:23 GMT

Could you provide an example?

To get a boolean (0 or 1) matrix, just use a logical expression with a matrix:

proc iml;
x = {1 2,
     1 3,
     2 4};
b = (x > 2);
print b;

The IF-THEN/ELSE statement works on a scalar quantity. The ANY function and ALL function can be used with the IF-THEN statement to make logical decisions. For example:

if any(x) > 3 then print "Some element > 3";
else print "No element > 3";

if all(x) > 0 then print "All elements > 0";
else print "Some element <= 0";

For more information, see "IF-THEN logic with matrix expressions."

Re: SAS IML IF/THEN/ELSE

abbaskashif — Wed, 18 Jan 2017 20:47:56 GMT

Given a matrix x below, I would like to have a resultant matrix y having 1 for each element of x<0  else 0:
proc iml;
x = {1 2,
 1 -3,
 2 4};

IF x<0 THEN y=1;
ELSE y=0;
print y;

Resultant matrix should be:
y=  {0 0,
     0 1,
     0 0}
The result however is a scalar y=0

Re: SAS IML IF/THEN/ELSE

Rick_SAS — Wed, 18 Jan 2017 20:53:42 GMT

As I explained in my previous response, don't use the IF-THEN statement. Just create the binary matrix:

proc iml;
x = {1  2,
     1 -3,
     2  4};

y = (x<0);
print y;