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calculate new mean from baseline and multiple visits using LAG

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Frequent Contributor
Posts: 142
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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;


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Solution
2 weeks ago
Super User
Posts: 10,046

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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Super User
Posts: 19,878

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

Try an approach using RETAIN instead.

Solution
2 weeks ago
Super User
Posts: 10,046

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;
☑ This topic is solved.

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