topic macro - meaning of % sign in SAS Programming

macro - meaning of % sign

HeatherNewton — Wed, 23 Mar 2022 13:15:28 GMT

Hi I am not familiar with the kind of macro where there is a % before a lot of words, what do they mean?

%macro gen_ind(num);
%do i=1 %to &num %by 1;
proc sql;
create table rate_MAC as select
a.*,
.
.
.
Quit;
%end;

Re: macro

MarkusWeick — Thu, 17 Mar 2022 06:29:44 GMT

Hi @HeatherNewton,

I recommend Chapter 1 "Introduction to the Macro Facility" in SAS 9.1 Macro Language.

I Think it's to difficult to explain yout example in two sentences.

Best, Markus

Re: macro

Kurt_Bremser — Thu, 17 Mar 2022 06:36:41 GMT

These are all Macro Statements

Re: macro

HeatherNewton — Thu, 17 Mar 2022 08:47:44 GMT

before I saw example where % are only added to %macro and %mend...

why suddenly they are added to do if then this kind of word?

Re: macro

Kurt_Bremser — Thu, 17 Mar 2022 08:54:26 GMT

@HeatherNewton wrote:

before I saw example where % are only added to %macro and %mend...

why suddenly they are added to do if then this kind of word?

Because these are macro statements. Please read the documentation.
In the link I gave you, go to Understanding and Using the Macro Facility. This will help you understand what the macro facility does.

Re: macro

MarkusWeick — Thu, 17 Mar 2022 08:58:07 GMT

Hi @HeatherNewton,

p.8. of the docu:

Conditionally creating SAS code gets to the point! It's an advanced concept. For me it helped to take the course SAS Training in the United States -- SAS® Macro Language 1: Essentials

Re: macro

HeatherNewton — Wed, 23 Mar 2022 08:58:58 GMT

am I right to say if these if then else loops in within a macro program, it needs % added to if then else?

if the if then else condition is not inside a macro program, then no % is required in from of if then else...

Re: macro

Kurt_Bremser — Wed, 23 Mar 2022 09:21:03 GMT

"&" and "%" are macro triggers which invoke the macro processor, or tell the macro processor that the following is (&) a macro variable/parameter reference , or (%) a macro statement or macro/macro function call. Everything else is just text to the macro processor.

You must first understand what the macro processor does. It is a code generator that allows you to create dynamic code. For easier understanding, its elements look a lot like "standard" SAS elements, but they are (in fact) completely different things.

IF and %IF are completely different things, although they have similarities, but THEY ARE DIFFERENT.

Same for (e.g.) SUBSTR vs. %SUBSTR.

Imagine you want to run a code for datasets that span back before Austria changed to the Euro, but, in case an "old" dataset is encountered, add a conversion to your code:

%if &year. lt 2002
%then %do;
amount = amount / 13.7604;
%end;

The first line compares the macro variable year to a value (mind - NOT a data step variable!!). If that comparison results in TRUE, the following %DO-%END block is executed by the macro processor, so it creates the code

amount = amount / 13.7604;

and feeds it back to the SAS data step compiler. In case you run the analysis for a later year, the statement is not created, and the data step compiler never sees it.

if year lt 2002
then do;
  amount = amount / 13.7604;
end;

This code does not invoke the macro processor, is "seen" by the data step compiler, and uses the data step variable year to make the comparison; the IF is always executed during data step runtime.