st: Sum over all possible combinations

["J E" <je_123@hotmail.com>]

Dear statalisters

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?

Thanks in advance

Julio

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