MATLAB: Distance between two point with the same value

distanceMATLAB and Simulink Student Suite

Hi,
I have a matrix like the one below and i need to get the mean distance between each 3, each 2 etc…
I tried to use several diastance function (like pdist etc) but none of these give an exploitable result (or maybe i misunderstood how its work).
Thank you for your help.
n=randi(3,10)
n =
     1     2     3     2     1     1     2     1     3     1
     2     1     3     2     1     3     1     1     2     3
     3     3     2     3     2     2     2     3     2     3
     1     1     2     2     1     1     3     1     1     3
     1     3     2     2     3     3     1     3     2     1
     1     1     1     3     1     3     1     3     2     1
     2     2     2     3     1     2     1     2     3     2
     3     2     2     2     1     1     1     2     2     3
     2     3     3     2     1     1     2     1     2     1
     2     1     3     2     2     2     2     2     3     1

Best Answer

Assuming euclidean distance metric:
n = randi(3, 10);   %demo input
vals = unique(n);  %get unique values in n
mdistances = zeros(size(vals));  %create storage for mean of distance for each unique value
for vidx = 1:numel(vals)   %iterate over each unique value
    [rows, cols] = find(n == vals(vidx));    %get location of all points with that unique value
    dist = hypot(rows - rows.', cols - cols.'); %calculate distance between each pair of point. Creates a symmetric matrix
    mdistances = mean(dist(tril(true(size(dist)), -1)));  %calculate mean of lower triangular matrix below diagonal of dist. i.e. distance between each unique pair of points
end
edit: spelling
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