CODEWITHSUNDEEP
matlabvectorization
reve_etrange
reve_etrange

Reputation: 2571

Find values in a matrix and put them into a vector

It must be simple, but surprisingly I couldn't find an answer to this problem here or by trial-and-error.
I want to get values out of a matrix (according to some condition) and place the values into a vector. I also need the subscript indices of the matching values. There is a lot of data so for loops are out.

This is a correct (but iterative) answer: 

[I,J] = find(A > 5);
values = zeros(numel(I),1);
for i=1:numel(I)
    values(i) = A(I(i),J(i));
end

I tried values = A(I,J) but this is n-by-n instead of n-by-1.

Upvotes: 3

Views: 2093

Answers (1)

Oliver Charlesworth
Oliver Charlesworth

Reputation: 272467

You can implicitly treat the matrix like a vector (linear indexing):

I = find(A > 5);
values = A(I);

Note that you can do this more efficiently with logical indexing:

values = A(A > 5);

Upvotes: 7

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