Pairwise difference between values of a vector

Question

Itai 2012-7-29

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https://ww2.mathworks.cn/matlabcentral/answers/44782-pairwise-difference-between-values-of-a-vector

回答： James Cai 2018-1-31

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

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Answer 1

the cyclist 2012-7-29

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https://ww2.mathworks.cn/matlabcentral/answers/44782-pairwise-difference-between-values-of-a-vector#answer_54860

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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