MATLAB: Apply Find to each row of an array

findMATLAB

I have an array of dimension [X Y], and I want to be able to efficiently apply the FIND function to each row of the array in order to find the location of the first non-zero index in each row.

By 'efficiently', I mean that I want to do so without having to go through a FOR loop – can I do so?

I understand there is a function ROWFUN, but I believe I would have to create a separate function that includes FIND in order to use that.

Thanks for any help.

Best Answer

Don't. That is not going to be efficient.

idx_first_nonzero = sum( cumprod(YourArray == 0, 2), 2) + 1;

Note: if any row is all-zero, this will return 1 longer than the array width. You have not defined a desired result for that case.

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MATLAB: Finding the indexes of first zero value in rows of a matrix

index_first_row_zero = sum( cumprod(logical(YourMatrix), 2), 2) + 1;

Note: in the case where none of the entries are 0, this returns one more than the width. You did not define the desired output for this case.

index_last_nonzero = size(YourMatrix,2) - sum( cumprod( ~logical(YourMatrix), 2, 'reverse'), 2);

Note: in the case where all of the entries are 0, this returns 0. You did not define the desired output for this case.

Best Answer

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