Re: st: data management question

[Daniel Feenberg <feenberg@nber.org>]

On Wed, 18 Sep 2013, Caroline Wilson wrote:

> Hello,
>
>  
>
> I’m wondering if someone can help with a data management
> question.
>
>  
>
> I’m trying to create a variable called “mean”, which, for a given 
> pat_ID, would be calculated by taking the mean of every other value of 
> “Md_T” in the same phy_ID EXCEPT for the current row. 

I am a little unclear on what you are asking - Md_T isn't in the sample 
data you show, but you want the mean of it? So I won't use your variable 
names. Nevertheless, I think that the -egen- -total- function and a 
generate statement will get you what you want:

  by ID: egen sum=total(var)
  generate sumex= sum-var
  by ID: generate meanex = sumex/(_N-1)

The total by ID gives the sum of var for each level of ID. Then we 
subtract the current level of var and divide by the number of observations 
in the ID group. (_N is the number of observations in the by group).

Daniel Feenberg