Sorting a sparse matrix according to matrix entries

Question

Milos 2023-3-15

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1929425-sorting-a-sparse-matrix-according-to-matrix-entries

评论： Milos 2023-3-16

I have a sparse matrix where I would like to sort the "list" according to the entries of the matrix. That is to say the first item in the list of the sorted sparse matrix would be the matrix position of the smallest vlaue of said matrix. To give an example;

spX =
   (3,2)       0.4190
   (2,4)       0.3872
   (6,4)       0.1841
   (5,5)       0.9246
   (6,6)       0.6273
   (7,6)       0.0216
   (4,7)       0.5755
  (10,9)       0.1069
   (2,10)      0.9397
   (6,10)      0.9456
   
   % A sparse matrix I have. After sorting one would hope to obtain;
   
   sort(spX) =
   
   (7,6)       0.0216
  (10,9)       0.1069
   (6,4)       0.1841
   (2,4)       0.3872
   (3,2)       0.4190
   (4,7)       0.5755
   (6,6)       0.6273
   (5,5)       0.9246
   (2,10)      0.9397
   (6,10)      0.9456
   
   %this is not the output that we get when we use sort.

I have tried the rowsort and sort function but neither yielded any fruit

Many Thanks,

Milos

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Answer 1

Walter Roberson 2023-3-15

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1929425-sorting-a-sparse-matrix-according-to-matrix-entries#answer_1193900

在 MATLAB Online 中打开

[r, c, s] = find(spX);
[s, idx] = sort(s);
out = [r(idx), c(idx), s]

You will not be able to get a sorted sparse matrix. You could reconstruct a sparse matrix with sparse(r(idx), c(idx), s) but it would just end up putting the entries back where they were before.