topic Re: Select from the first to the k-th element in a macro list variable in New SAS User

Select from the first to the k-th element in a macro list variable

AndreMenezes — Fri, 04 Jan 2019 00:29:52 GMT

Dear all,

Suppose that I have the following macro list variable:

%let list = a1, a2, a3, a4, a5;

If I want to create another macro variable selecting the elements a1, a2 and a3 how can I do this?

Thanks.

AFM.

Re: Select from the first to the k-th element in a macro list variable

Astounding — Fri, 04 Jan 2019 01:15:19 GMT

You really turned this into a difficult problem by inserting commas into your list. Is there any chance you can go back and change the code so that you get:

%let list = a1 a2 a3 a4 a5;

Re: Select from the first to the k-th element in a macro list variable

ChrisBrooks — Fri, 04 Jan 2019 01:37:02 GMT

I agree with @Astounding it's easier without the commas - then check out the %scan macro function which allows you to select the nth element from the list, put that inside a %do loop and you're done....

Re: Select from the first to the k-th element in a macro list variable

Astounding — Fri, 04 Jan 2019 02:31:25 GMT

If you need to keep the commas, here's a trick that might work. (I can't test it at the moment so that part is up to you).

%let list = a1, a2, a3, a4, a5;

%macro first3;

%global newmacrovar;

%let newmacrovar=;

%local k;

%do k=1 %to 3;

%let newmacrovar = &newmacrovar %scan("&list", &k, ", ");

%end;

%mend first3;

I'm omitting the commas from the new macro variable, but they can be added with a single additional line of code:

%do k=1 %to 3;

%let newmacrovar = &newmacrovar %scan("&list", &k, ", ");

%if &k < 3 %then %let newmacrovar = &newmacrovar,;

%end;

Re: Select from the first to the k-th element in a macro list variable

Ksharp — Sat, 05 Jan 2019 10:52:21 GMT

%let list = a1, a2, a3, a4, a5;
%let want=%sysfunc(prxchange(s/\W+\w+\W+\w+$//,1,%nrbquote(&list)));

%put &want ;

Re: Select from the first to the k-th element in a macro list variable

AndreMenezes — Sat, 05 Jan 2019 21:30:24 GMT

Thank you very much for your answer!

Re: Select from the first to the k-th element in a macro list variable

AndreMenezes — Sat, 05 Jan 2019 21:33:11 GMT

I appreciate your solution.
I solved the problem using the %do loop, but I thought there were some function like scan that select the k-th element from a list macro variable.