数据步骤中宏变量的解析

Question

I'm having trouble getting If/Then statements to work correctly with my macro variables inside a datastep. I'm writing a macro to handle two different cases: calculating stat tests with no transformation, and then calculating stat tests after a natural log transformation. If my data fails the test of normality, I log transform and test again. If it passes, I set my global flag, log_flag , to 1. I then want to test the status of this flag in data steps in order to correctly handle the transformed (or not) variables. I've tried variations of the following:

Data want;
set have;
if symget("log_flag")=1 then do;
if &log_flag. = 1 then do;
if resolve("log_flag")=1 then do;
test=symget("log_flag");
  if test=1 then do;
end

No matter what I try, the if/then statement is essentially ignored and all code following it is processed as if the if/then were true, even when it is false. I know that the log_flag is being correctly assigned a value of zero because the %if %then statements work and execute correctly in open code. I'm just having trouble getting it to resolve correctly inside a datastep.

Please let me know if there is any other information you need to help me figure this out. Thanks guys!

Answer 1

The issue you have identified in the comments is that you do not want to generate the SAS code at all. That is what the macro language processor is for. So use %IF to conditionally generate the code.

So if you only want to create the variable newvar when the macro variable log_flag is one then you could code it this way.

data want ;
  set have ;
%if &log_flag. = 1 %then %do;
  newvar= x*y ;
%end;
run;

So when &log_flag. = 1 &log_flag. = 1 you run this code:

data want ;
  set have ;
  newvar= x*y ;
run;

And when it isn't you run this code:

data want ;
  set have ;
run;

Starting with SAS 9.4 M5 release you can use this in open code, otherwise place it inside a macro definition and execute the macro.

Answer 2

• SYMGET() will return a character variable.
• RESOLVE() will return a character variable, but it needs the & in the parameter.
• &log_flag will resolve as numeric

You need to treat them correctly depending on your reference method.

Here's an example of testing each one independently and then you can test them together via nesting if desired.

%let log_flag=1;
Data want;
set sashelp.class;
if symget("log_flag")='1' then do;
  put "Test #1 is True";
end;

if &log_flag. = 1 then do;
  put "Test #2 is True";
end;


if resolve("&log_flag")="1" then do;
  put "Test #3 is True";
end;

test=symget("log_flag");
if test='1' then do;
  put "Test #4 is True";
end;

run;