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GKati
Pyrite | Level 9

Hello, 

 

I have an UNBALANCED PANEL  of clients (i.e. not all clients are present on every year) for four years (2010-2013). I would like to calculate the change in costs over the years. The problem is that when I lag the variable "costs", SAS lags over all client numbers (i.e. 2013 of client1 will become 2010 for client2). How do I prevent this from happening?

 

I can't just take out year=2010, because for some clients 2011 was the first year.

 

This is what I have so far:

 

data costchange;

set sample;

by cient;

lcost=lag(cost);

cost_score = (cost - lcost)/lcost;

where treated=1;

 

run;

1 ACCEPTED SOLUTION

Accepted Solutions
Astounding
PROC Star

When using LAG, it's important to make sure it executes on every observation.  You're doing that ... so far so good.

 

The trick is to wipe out the value for observations that begin a new CLIENT.  So:

 

data costchange;

set sample;

by cient;

lcost=lag(cost);

if first.client then lcost = . ;

cost_score = (cost - lcost)/lcost;

where treated=1;

run;

View solution in original post

3 REPLIES 3
RW9
Diamond | Level 26 RW9
Diamond | Level 26

As always, some test data in the form of a datastep would help clarify what you mean.  At a guess, maybe use retain'd variables and set them once per group, then when missing use the retained variable.

Astounding
PROC Star

When using LAG, it's important to make sure it executes on every observation.  You're doing that ... so far so good.

 

The trick is to wipe out the value for observations that begin a new CLIENT.  So:

 

data costchange;

set sample;

by cient;

lcost=lag(cost);

if first.client then lcost = . ;

cost_score = (cost - lcost)/lcost;

where treated=1;

run;

GKati
Pyrite | Level 9

Perfect! Just what I was looking for. 

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