## calculate new mean from baseline and multiple visits using LAG

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Regular Contributor
Posts: 182

# calculate new mean from baseline and multiple visits using LAG

[ Edited ]

I'm trying to calculate the change in mean from baseline to each visit (vist1 to vist2; vist1 to visti3; visit1 to visit4...)

I tried this using lag, but results don't seem correct.  It is just using the lag between observations rather than holding visit 1 as the LAG.  Help is appreciated

Starting:

 visit mean 1 2.41 2 2.47 3 2.53 4 2.54

want something like this:

 visit mean change 1 2.41 . 2 2.47 2.44 3 2.53 2.47 4 2.54 2.48

I started with this code:

data want;

set have;

lag_mean=lag(mean);
change=mean-lag_mean;
run;

Accepted Solutions
Solution
‎11-13-2017 07:50 PM
Super User
Posts: 10,778

## Re: calculate new mean from baseline and multiple visits using LAG

``````data have;
input visit	mean;
cards;
1	2.41
2	2.47
3	2.53
4	2.54
;
run;

data want;
set have;
sum+mean;
change=sum/_n_;
if _n_=1 then change=.;
drop sum;
run;``````

All Replies
Super User
Posts: 23,713

## Re: calculate new mean from baseline and multiple visits using LAG

Try an approach using RETAIN instead.

Solution
‎11-13-2017 07:50 PM
Super User
Posts: 10,778

## Re: calculate new mean from baseline and multiple visits using LAG

``````data have;
input visit	mean;
cards;
1	2.41
2	2.47
3	2.53
4	2.54
;
run;

data want;
set have;
sum+mean;
change=sum/_n_;
if _n_=1 then change=.;
drop sum;
run;``````
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