# Re: st: How to calculate mean of other individuals on the same group

 From Ryan Herzog To statalist@hsphsun2.harvard.edu Subject Re: st: How to calculate mean of other individuals on the same group Date Tue, 13 Feb 2007 21:04:24 -0800

```Quang Nguyen wrote:
```
Dear all,

A simplified version of my data looks as follows:

ID Group X
1 a 5
2 a 7
3 a 9
4 a 8
5 b 3
6 b 4
7 b 9
..........................

I would like to generate a new variable whose value is the average of
other individual in the same group as the concerned individual. For
example, for the first individual (ID=1), this will be: (7+9+8)/3= 8.
For the 6th individual, this will be (3+9)/2=6 and so on.

I would highly appreciate if someone could suggest me a solution for this.
Thanks and Have A Great Day!
Sincerely yours,

Quang
*
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Generate the sum of each group: egen sum_var = sum(X), by(group)
Subtract the X value for that Id: gen sum_less = sum_var - X
Generate a count variable by group: egen count_var = count(X), by(group)
Subtract one from count, to exclude the ID's observation: gen count_less = count_var - 1
gen mean_X = sum_less / count_less

Ryan
*
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* http://www.ats.ucla.edu/stat/stata/