topic Retaining Values in a Do Loop in SAS Programming

Retaining Values in a Do Loop

Scott_Mitchell — Mon, 02 Jun 2014 10:07:22 GMT

Hi Guys,

I am sure there is a very good reason for this, but I can't seem to get it through my thick head at 2am.

Why, when I run the below code, am I retaining the value of the previous OBS when I concatenate using the 3 arguments below?

DATA ENROLLMENT;

ATTRIB GROUP_ID LENGTH = $400;

DO ID = 1 TO 10;

DO J = 1 TO 1;

GROUP_ID = CATS(GROUP_ID,ID,"P");

END;

OUTPUT;

END;

RUN;

It is driving me nuts. Sorry to ask such a newbie question.

Regards,

Scott

Re: Retaining Values in a Do Loop

Kurt_Bremser — Mon, 02 Jun 2014 10:17:24 GMT

The data step variables are set to missing only when the complete data step enters its next iteration (think of the jump from "run" to "data"). Between "data" and "run" (or whatever begins the next SAS program step) the variables keep their values, no matter how many SET or OUTPUT statements you have.

Re: Retaining Values in a Do Loop

RW9 — Mon, 02 Jun 2014 10:21:27 GMT

Yep, it looks like the last value is being held over in memory after the output statement. Pop a clean statement in after the output, would need to check the documentation as to exactly what it is doing:

DATA ENROLLMENT;

ATTRIB GROUP_ID LENGTH = $400;

DO ID = 1 TO 10;

DO J = 1 TO 1;

GROUP_ID = CATs(GROUP_ID,ID,"P");

output;

group_id="";

END;

RUN;

Re: Retaining Values in a Do Loop

Keith — Mon, 02 Jun 2014 11:24:06 GMT

I believe you can also get around this by using the CALL CATS function.

DATA ENROLLMENT;

ATTRIB GROUP_ID LENGTH = $400;

DO ID = 1 TO 10;

DO J = 1 TO 1;

CALL CATS(GROUP_ID,ID,"P");

END;

OUTPUT;

END;

RUN;

Re: Retaining Values in a Do Loop

Scott_Mitchell — Tue, 03 Jun 2014 05:05:50 GMT

Thanks everyone.