Lag function in SAS

cindyforest7 — Wed, 29 Apr 2015 14:25:45 GMT

Dear All,

I'm working on a project where I need to establish inferred referral relationships between PCPs and specialists. The way I defined inferred referrals is that if member A visited a PCP followed by a specialist visit within 30 days then there is an inferred referral relationship between that PCP and speclialist.

So I have a dataset with all historical visit information for a bunch of members.

member_id visit_date provider_id provider_type

a 1/1/2014 A PCP

a 1/26/2014 B Specialist

a 2/30/2014 A PCP

a 3/2/2014 B Specialist

b 5/16/2014 C PCP

b 7/02/2014 D Specialist

b 7/27/2014 C PCP

b 8/15/2014 C PCP

b 8/19/2014 D Specialist

... ... ... ...

And I want to produce a referral table containing all the inferred referral relationships among PCP and specialists for all members

member_id PCP Specialist

a A B

b C D

If member a visited specialist B within 30 days after visiting PCP A, then there will be a referral link between A and B.

I've written some codes

Data want;

set have;

prior_provider=lag(provider_id);

prior_date=lag(visit_date);

if prior_provider=provider_id then delete;

if prior_provider=. then delete;

run;

However, the codes won't pair a PCP with a specialist that a member didn't subsequently visited but within 30 days of visiting that PCP. For example, a member visited PCP A and then specialist B within 30 days and then spelialist C also within 30 days, the codes will only establish a link between A and B, but not A and C.

Any help and inputs would be much appreciated!!!!

Thanks a bunch!

Re: Lag function in SAS

Haikuo — Wed, 29 Apr 2015 14:50:48 GMT

LAG() may not be what you need. Try the following code as a starter:

data have;

input member_id $ visit_date :mmddyy10. provider_id:$2. provider_type:$20.;

format visit_date :mmddyy10.;

cards;

a 1/1/2014 A PCP

a 1/26/2014 B Specialist

a 2/28/2014 A PCP

a 3/2/2014 B Specialist

b 5/16/2014 C PCP

b 7/02/2014 D Specialist

b 7/27/2014 C PCP

b 8/15/2014 C PCP

b 8/19/2014 D Specialist

;

proc sql;

create table want as

select distinct a.member_id, a.visit_date, a.provider_id as PCP, b.provider_id as Specialist

from have (where=(UPCASE(provider_type)='PCP')) a

left join have (where=(upcase(provider_type)='SPECIALIST')) b

on a.member_id=b.member_id

and (b.visit_date - a.visit_date) between 0 and 30

;

quit;

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Lag function in SAS

Re: Lag function in SAS