topic Re: How do I keep the first observation conditioned upon 2 variables? in SAS Programming

How do I keep the first observation conditioned upon 2 variables?

cbatzi01 — Fri, 21 Oct 2016 22:19:03 GMT

Hi,

I have pharmacy claims data. I would like to keep the first record for each patient and each drug based on fill date. My data look like this:

Patid Drug Fill_date

Normally, if I was interested in only 1 drug, i would only keep those records, and then I would sort by patid and fill_date, then do something like this:

proc sort data=have; by patid drug fill_date; run;

data want;

data have;

by patid

if first.patid=1;

run;

But since I need the first patid AND drug, that will not work. How would this be done if I sorted by patid, drug, and fill_date?

Thanks!
Chris

Re: How do I keep the first observation conditioned upon 2 variables?

Reeza — Fri, 21 Oct 2016 22:04:35 GMT

You want each each new instance of drug in this case, so change your FIRST to be relative to the drug variable.

if first.drug;

Make sure your BY statement has at least both variables.

Re: How do I keep the first observation conditioned upon 2 variables?

cbatzi01 — Fri, 21 Oct 2016 22:18:05 GMT

Sorry, I need the first of the drug for each unique patient ID. Does your method still work with that requirement?

Thanks!
Chris

Re: How do I keep the first observation conditioned upon 2 variables?

Reeza — Fri, 21 Oct 2016 22:23:25 GMT

Try it and let me know.