topic Re: Extracting patients based on number of observations in SAS Data Management

Extracting patients based on number of observations

sarahsasuser — Fri, 30 Jun 2017 14:03:50 GMT

Hi All,

I have a data set of patient visits. We want to extract only the patients who have at least 2 visits. How do I do this?

Have:

id visit#

a 1

a 2

a 3

a 4

b 1

c 1

c 2

c 3

d 1

The data set I want would only include ids a and c.

Thanks!

Re: Extracting patients based on number of observations

FredrikE — Fri, 30 Jun 2017 14:16:08 GMT

Something like this?

data test;

length id visit $1;

input id visit;

datalines;

a 1

a 2

a 3

a 4

b 1

c 1

c 2

c 3

d 1

;

run;

proc sql;

create table sel as

select id

from test

group by id

having count(visit) > 1

;

quit;

data test1;

merge test (in=a) sel (in=b);

by id;

if a and b;

run;

//Fredrik

Re: Extracting patients based on number of observations

RW9 — Fri, 30 Jun 2017 14:24:57 GMT

data want;
  set have;
  by id;
  if if first.id and last.id then delete;
run;

Removes any records where there is only one recor per id.

Re: Extracting patients based on number of observations

FredrikE — Fri, 30 Jun 2017 14:26:39 GMT

Sweet!

Re: Extracting patients based on number of observations

sarahsasuser — Fri, 30 Jun 2017 14:29:27 GMT

I like it, but we may decide we want to include people with more observations down the line. I think I'll try FredrikE's method. Thanks!

Re: Extracting patients based on number of observations

FredrikE — Fri, 30 Jun 2017 14:33:39 GMT

Replace my merge with:
Proc sql;
Create table new as select a.* from test as a inner join visits as b on a.id = b.id; quit;
Then you don not need to have data sorted.