Count number of rows in a matrix based on frequency of one element and value of another element

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Neuro 2022-1-17

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https://ww2.mathworks.cn/matlabcentral/answers/1630660-count-number-of-rows-in-a-matrix-based-on-frequency-of-one-element-and-value-of-another-element

评论： Neuro 2022-1-17

Hello. I'm quite rusty with Matlab and was wondering if anyone could help me with this. Let's say you have a 2000 x 2 matrix, where all the elements are integers. How can we count the number of rows that have the number 10 in the first column and any number greater than 5 in the second column?

I tried this, but didn't work:

numel(matrix(matrix(:,1) == 10) & matrix(matrix(:,2) > 5));

Thanks for your help!

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Answer 1

Matt J 2022-1-17

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https://ww2.mathworks.cn/matlabcentral/answers/1630660-count-number-of-rows-in-a-matrix-based-on-frequency-of-one-element-and-value-of-another-element#answer_876245

编辑：Matt J 2022-1-17

在 MATLAB Online 中打开

nnz( matrix(:,1) == 10 & matrix(:,2) > 5 );

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Neuro 2022-1-17

Thanks! Didn't know the nnz function! :)

Neuro 2022-1-17

@Matt J Sorry, I just realised that this won't work as I need to count the zeroes as elements. Is there a way to do the same thing but counting the zeroes as ones? After all, I need to count the number of elements and zeroes are still elements.

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