Testing for an empty parameter in a SAS Macro

Question

For example, i have a macro program

%macro test(parameter1= , parameter2=, parameter3=);
  DATA data_gender;
  SET data_input(WHERE=(gender=parameter3));
           


        

Answer 1

Agree with Joe's answer. One good point they make in the paper is they are testing for blank, and their test will return true whether a parameter is null or has blanks in it. Sometimes it is useful have a test that differentiates between a parameter that is null and one that has blanks. The paper mentions %length(%superq( )) as a possible test for null. For example below, this allows you to specify a blank value for sex, and get a different result than you do when sex is null.

data class;
  set sashelp.class;
  if _n_=1 then sex='';
run;

%macro test2(parameter1= , parameter2=, sex=);
  DATA data_gender;
  SET class(
            %if %length(%superq(sex)) %then %do;
              where=(sex="&sex.")
            %end;
           );
  RUN;
%mend;

%test2(sex=)
%test2(sex=%str( ))