topic Do loop in SAS Programming

Do loop

vincentgoh88 — Tue, 29 May 2018 12:08:03 GMT

Hi,

Can anyone help me to understand why the final output x= 5 index = 7 appear?

Code:


data work.loop;
	x = 0;
	do index = 1 to 5 by 2;
	x = index;
	output;
	end;
	output;
run;

Output:

Re: Do loop

RW9 — Tue, 29 May 2018 12:18:00 GMT

Just simply follow the logic:

	do index = 1 to 5 by 2;
	x = index;
	output;
	end;
	output;

Index starts at 1, x is set to it. Then it is output

Then 3, x is set to it. Then it is output

Then 5, x is set to it, then it is output.

Then index becomes 7, which does not work in the do, so the do loop is jumped, and then next step is output, which outputs the 7 record. X remains as 5, as the part in the do loop is not executed.

Re: Do loop

vincentgoh88 — Tue, 29 May 2018 12:22:27 GMT

Thanks!

Re: Do loop

Amir — Tue, 29 May 2018 12:27:05 GMT

Hi,

The do loop continues looping until the upper limit is exceeded, so after the loop has processed the index of 5, index is increased by 2 which becomes 7 which exceeds the upper limit of the loop and so it is not executed again; x is not reassigned again so it is left with its last value of 5.

Regards,

Amir.

Re: Do loop

Ksharp — Tue, 29 May 2018 12:53:03 GMT

After DO LOOP ,index will +2 by itself , therefore, the last index is 7 .

Re: Do loop

Kurt_Bremser — Tue, 29 May 2018 13:17:02 GMT

Basically all languages that I know implement iterative loops like that.

Only loops where the "index variable" is set from a list (eg see "for" in UNIX shell scripting) terminate differently.