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st: RE: Sum over all possible combinations


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Sum over all possible combinations
Date   Sun, 22 Jul 2007 18:41:24 +0100

This sounds like 

	number in group * Gini mean difference * 2 

As the second L-moment is 

	Gini mean difference / 2 

-lmoments- from SSC will get you most of the way 
there. 

For example, 

lmoments varname, by(group) gen(n=n sad=l2) 
replace sad = 4 * n * l2 

Check this out with hand-calculations for a toy example. 

Nick 
n.j.cox@durham.ac.uk 

Julio E
 
> I am interested in computing the sum of the absolute value of 
> all possible 
> differences within a group of my sample.
> 
> Suppose that the variable "group" denotes the variable 
> indicating the group 
> to which an individual belongs and Y is an outcome variable. 
> I am interested 
> in computing
> 
> sum of abs (Yi-Yj) for all i and j  belonging to group K
> 
> My programming skills are almost none. Can somebody help me 
> out regarding an 
> efficient way of computing such statistic?

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