How to delete nonzero values at the end of a matrix

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Mister Finance 2021-8-13

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https://ww2.mathworks.cn/matlabcentral/answers/897597-how-to-delete-nonzero-values-at-the-end-of-a-matrix

评论： Mister Finance 2021-8-13

Assume I have the following array:

M = [1 1 1; 0 2 2; 3 3 0; 4 4 0; 0 5 0]
M = 5×3
   1     1
   2     2
   3     0
   4     0
   5     0

How do I set all elements from the end of each row to the first nonzero value to NaN?

The result should look like this:

M = [1 1 1; 0 2 2; 3 3 NaN; 4 4 NaN; NaN 5 NaN]
M = 5×3
     1     1     1
     0     2     2
     3     3   NaN
     4     4   NaN
   NaN     5   NaN

It is important that only the zero values at the end are set equal to NaN and not all elements that are equal to zero.

Thank you!

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Answer 1

Chunru 2021-8-13

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https://ww2.mathworks.cn/matlabcentral/answers/897597-how-to-delete-nonzero-values-at-the-end-of-a-matrix#answer_766227

在 MATLAB Online 中打开

M = [1 1 1; 0 2 2; 3 3 0; 4 4 0; 0 5 0]
M = 5×3
     1     1     1
     0     2     2
     3     3     0
     4     4     0
     0     5     0
for i=1:size(M, 2)
    idx = find(M(:, i), 1, 'last');
    M(idx+1:end, i) = nan;
end
M
M = 5×3
     1     1     1
     0     2     2
     3     3   NaN
     4     4   NaN
   NaN     5   NaN
%M = [1 1 1; 0 2 2; 3 3 NaN; 4 4 NaN; NaN 5 NaN]