Diagonal Elements of the Square Matrix

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MByk 2017-10-7

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编辑： MByk 2017-10-7

I am calculating Sorensen-Dice coefficient (2|A and B|/|A|+|B|) but diagonal elements (intersection with itself) of the square matrix is equal to zero. It is not a big problem but how can I convert them into ones. Thanks for the help.

v = [1 1 0 0 1 1 0; 1 1 0 1 0 0 0; 0 0 0 0 0 1 1]
d = squareform(pdist(v,@(a,b)(2 * sum((a.*b),2))./(sum(a) + sum(b,2))));

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Answer 1

John D'Errico 2017-10-7

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在 MATLAB Online 中打开

If the diagonal is already EXACTLY zero, then this will suffice:

M = M + eye(size(M));

If they are only approximately zero, then you could do this:

M(find(eye(size(M)))) = 1;

For example,

M = magic(5)
M =
  17    24     1     8    15
  23     5     7    14    16
   4     6    13    20    22
  10    12    19    21     3
  11    18    25     2     9
M(find(eye(size(M)))) = 1;
M
M =
   1    24     1     8    15
  23     1     7    14    16
   4     6     1    20    22
  10    12    19     1     3
  11    18    25     2     1