topic Re: flag participants with multiple observations in SAS Programming

flag participants with multiple observations

JLang055 — Sat, 19 Nov 2022 15:25:15 GMT

Hello. I have a patient dataset with observations by participant. I want to flag participants with multiple observations in the dataset. See below for an example.

FID	Flag (want)
1	1
1	0
2	0
3	0
4	1
4	0
4	0
5	0

Re: flag participants with multiple observations

Kurt_Bremser — Sat, 19 Nov 2022 17:01:06 GMT

data want;
set have;
by fid;
flag = (first.fid and not last.fid);
run;

Re: flag participants with multiple observations

JLang055 — Sun, 20 Nov 2022 21:55:54 GMT

Thanks @Kurt_Bremser. It seems that your code flagged the first observation for every participant. Is there a way to change the code so that it only flags those with multiple observations. If a participant has only one observation I dont want them flagged.

Re: flag participants with multiple observations

Kurt_Bremser — Mon, 21 Nov 2022 06:17:24 GMT

Simply cannot be with the data you posted and my code:

data have;
input fid;
datalines;
1
1
2
3
4
4
4
5
;

data want;
set have;
by fid;
flag = (first.fid and not last.fid);
run;

proc print data=want noobs;
run;

Result:

Matches exactly with your expected result from your initial post:

FID Flag (want)

1 1

1 0

2 0

3 0

4 1

4 0

4 0

5 0