MATLAB: What does A(~A) mean

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could someone tell me what does following code mean please?

A(~A)=inf; %A is a vector with zero and non-zero numbers.

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Best Answer

It works out the same as

A(A~=0) =inf

Which is to say that it replaces all nonzero entries with infinity.

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MATLAB: What does NaN mean here

Looks like the code intended to initialize a matrix filled with NaNs and does this by adding NaN to a zero matrix. Any number + NaN is NaN.

You could achieve the same effect with:

aux = NaN(colK);

One common reason you would use NaN instead of 0 is to differentiate when you actually have a value of 0 (say 0 Celsius) versus you have no idea what that value is.

MATLAB: What does fidelity mean

%mu says whether the E values bear the same relationship to each other that the M values do
mu(i,j) = sign( E(D(i)) - E(D(j)) ) == sign( M(D(i)) - M(D(j)) )

However, we do not have enough information about the meaning of E or M to fully optimize the computation. I suspect it might be possible to do all of the comparisons at the same time over an array, zero the diagonal, sum the result, divide by n*(n-1), multiply by 100 -- the 2 would cancel in such an implementation, I think.

mu = sign(bsxfun(@minus, E(:), E(:).')) == sign(bsxfun(@minus, M(:), M(:).'));
n = size(mu,1);
mu(1:n+1:end) = 0;   %zero diagonal
F = 100 * sum(mu(:)) / (n*(n+1));

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MATLAB: What does NaN mean here

MATLAB: What does fidelity mean

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