topic Re: Do Loop need to stop at the end in SAS Programming

Do Loop need to stop at the end

hhchenfx — Sat, 18 Dec 2021 18:34:15 GMT

Hi,

My code below look back 3 row and count number of value positive.

It works quite fine except for the last rows of where the value is maxed at 4.

I try to do the "do n=_n_ to _n_+3 UNTIL eof" but fail.

Can you please help to fix it?

Thanks,

HHC

data h;
input Year_Month State $ Value;
datalines;
201401 CA -1
201402 CA .
201403 CA 2
201404 CA 5
201405 CA 8
201405 CA 2
201401 TX 1
201402 TX -4
201403 TX .
201404 TX 4
201405 TX 3
201405 TX 1
;


data w;
keep Year_Month state value c ;
set h nobs=totalobs;
c=0;
if value>0 then do;
	do n =_n_ to _n_+3;
		set h(rename =(Year_Month =ym state=st value=vl )) point=n;
		if st=state and vl>0 then c=c+1;
	end;
end;
run;

Re: Do Loop need to stop at the end

Tom — Sat, 18 Dec 2021 19:04:40 GMT

Your code appears to be looking ahead, not back.

You want to look at the current and three following observations?

do pointer=_n_ to min(_n_+3,totalobs);
  set h(....)  point=pointer;
  ...
end;

If you want to look back you could use LAG() function. Or you could modify your DO loop.

do pointer=_n_ to max(_n_-3,1) by -1;
  set h(....)  point=pointer;
  ...
end;

Re: Do Loop need to stop at the end

hhchenfx — Sat, 18 Dec 2021 19:57:12 GMT

Hi Tom,

Thanks for your comment.

I actually didn't know how to do look back and I got to do Sort before lol.

HHC