Pairwise difference between values of a vector

Hello all, I want to calculate the mean of all absolute pairwise differences (Ei-Ej) from a long set of values. for example (3 1 2) the differences are 3-1=2, 3-2=1, 1-2=1 and the mean (2+1+1)/3=1.33. Thanks for helping

Answer 1

[the cyclist]

One way:

% The data
v = [3 1 2];

% Number of elements
nv = numel(v);

% Absolute pairwise diifferences
dv = abs(bsxfun(@minus,v,v'));

% Sum the differences (This double-counts, but we'll double-count the denominator, too)
sdtv = sum(dv(:));

% Number pairs (also double-counted)
np = nv^2 - nv;

% The mean
mdtv = sdtv/np

Answer 2

[James Cai]

Nowadays, dv = abs(v-v') returns the absolute pairwise differences.