find sum of all the entries with value 0

3 次查看（过去 30 天）

arun 2013-11-29

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/108022-find-sum-of-all-the-entries-with-value-0

评论： Jos (10584) 2013-12-2

I have a cell matrix of mat = [ 1 0 0 4;0 2 0 4], i want to find the sum of the all the entries having value 0. in the case of given example the entries having count 0 are 4; so sum will be 4. how can i do this.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Matt J 2013-11-29

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/108022-find-sum-of-all-the-entries-with-value-0#answer_116719

编辑：Matt J 2013-11-29

在 MATLAB Online 中打开

sum(~mat(:))

3 个评论
显示 1更早的评论隐藏 1更早的评论

Matt J 2013-11-29

编辑：Matt J 2013-11-29

在 MATLAB Online 中打开

No, what I proposed

sum(~mat(:))

works indepedently of ndims(mat) and will save you additional function calls to sum().

arun 2013-11-30

okieee,sorry............... i got it.

请先登录，再进行评论。

更多回答（1 个）

Jos (10584) 2013-11-30

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/108022-find-sum-of-all-the-entries-with-value-0#answer_116800

在 MATLAB Online 中打开

NNZ is the dedicated function to do this:

nnz(~mat)

3 个评论
显示 1更早的评论隐藏 1更早的评论

John D'Errico 2013-11-30

Note that nnz(~mat) will be poor even for large sparse matrices, because if mat is sparse, then ~mat must create a large and rather dense logical matrix. Better then would be to use a form like:

numel(mat) - nnz(mat)

In my tests, for a large fairly sparse matrix like that generated by Matt in his comment, my form was the fastest.