topic Re: Creating a (macro) variable from a macro variable containing a list of variables in SAS Programming

Creating a (macro) variable from a macro variable containing a list of variables

alexgonzalez — Wed, 14 Oct 2020 19:12:43 GMT

Hello,

I want to create a macro that needs to identify whether a macro variable previously defined contains certain variable. For example, I first created the macro variable 'covariates' as shown below:

%let covariates = seq weekend sex;

Then, the following macro runs a block of code depending whether the variable 'sex' is included in &covariates or not (See red text below).

%macro test;

*The two lines of code below are to show what I, not how;
"if &covariates contains SEX" then &sex=1;
else &sex=0;

%if %sysevalf(&sex=1) %then %do;
%end;

%else %do;
%end;

%mend;

Can you please advice?

Thanks a lot.

Re: Creating a (macro) variable from a macro variable containing a list of variables

Reeza — Wed, 14 Oct 2020 19:18:05 GMT

Where will this occur? Within a data step, SQL or open code? What should happen in the end, a new variable is being created or a new macro variable? What is the macro variable sex coming from and what value does that contain? Why the duplicate logic as well, is there a specific reason to create that variable rather than go straight into the IF/THEN logic?

As to isolating terms, you can use regular functions like FIND but you need to use SYSFUNC() within the macro language.

Re: Creating a (macro) variable from a macro variable containing a list of variables

RichardDeVen — Wed, 14 Oct 2020 19:33:53 GMT

Use the base function INDEXW to detect the position of a word in a delimited list of words. If not found the result will be zero, so you can use the result as a logical test for presence.

INDEXW is case sensitive so you need to be careful.

Example

%let itemlist = seq weekend sex;
%put NOTE: token SEX at position %sysfunc(indexw(%upcase(&itemlist),SEX));
%put NOTE: token WEEKDAY at position %sysfunc(indexw(%upcase(&itemlist),WEEKDAY));

Log

NOTE: token SEX at position 13
NOTE: token WEEKDAY at position 0

Re: Creating a (macro) variable from a macro variable containing a list of variables

alexgonzalez — Thu, 15 Oct 2020 11:33:10 GMT

Thanks Richard, that's exaclty what I needed.

Re: Creating a (macro) variable from a macro variable containing a list of variables

alexgonzalez — Thu, 15 Oct 2020 11:38:57 GMT

Hi Reeza,
The variable 'SEX' is specified in a previous part of my code as a covariate in a regression model. In the new macro I'm referring to, I wanted to decide which block of code to run. That's to say, if 'SEX' is part of the covariates in the model, then run a block, else run the other one. I tried the FIND function, but I could not get the answer I needed. I wasn't sure who to make work in my example. See reply by RichardAdeVenezia, that worked for me.
Thank you!