Distance between two point with the same value

Question

Silnae 2019-11-18

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/491674-distance-between-two-point-with-the-same-value

编辑： Guillaume 2019-11-18

采纳的回答： Guillaume

在 MATLAB Online 中打开

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 =
   2     3     2     1     1     2     1     3     1
   1     3     2     1     3     1     1     2     3
   3     2     3     2     2     2     3     2     3
   1     2     2     1     1     3     1     1     3
   3     2     2     3     3     1     3     2     1
   1     1     3     1     3     1     3     2     1
   2     2     3     1     2     1     2     3     2
   2     2     2     1     1     1     2     2     3
   3     3     2     1     1     2     1     2     1
   1     3     2     2     2     2     2     3     1

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Turlough Hughes 2019-11-18

How are you defining distance?

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Answer 1

Guillaume 2019-11-18

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/491674-distance-between-two-point-with-the-same-value#answer_402020

编辑：Guillaume 2019-11-18

在 MATLAB Online 中打开

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