Sorting elements of a matrix ignoring NaN

Question

Stephen 2016-3-21

1
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/274788-sorting-elements-of-a-matrix-ignoring-nan

编辑： Azzi Abdelmalek 2016-3-21

采纳的回答： Azzi Abdelmalek

在 MATLAB Online 中打开

Dear All,

I have the following 4x4 matrix have containing numbers and NaN:

have = [5 NaN  4   9;
        4  0  NaN  9;
       -6 NaN  2   3;
        1  7  NaN -3]

I would like to assign a rank (ascending/descending) to the elements of each colum of the matrix have. In the sorting procedure, the NaNs should be ignored and elements with the same value (column 4) should have the same (tied) rank.That is, I would like to obtain the following matrices:

want_ascend = [4  NaN  2   3; 
               3   1  NaN  3;
               1  NaN  1   2;
               2   2  NaN  1]
want_descend = [1  NaN  1   1;
                2   2  NaN  1;
                4  NaN  2   2;
                3   1  NaN  3]

My attempt involving the sort function does not successfully ignore the NaN (which are ranked too).

[~,attempt]=sort(have,1,'descend')
attempt =
     1     1     2     1
     2     3     4     2
     4     4     1     3
     3     2     3     4

Any help would be highly appreciated. Thanks!

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Answer 1

Azzi Abdelmalek 2016-3-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/274788-sorting-elements-of-a-matrix-ignoring-nan#answer_214516

编辑：Azzi Abdelmalek 2016-3-21

在 MATLAB Online 中打开

have = [5 NaN  4   9;
      4  0  NaN  9;
     -6 NaN  2   3;
      1  7  NaN -3]
  idx=isnan(have)
  [n,m]=size(have)
  [have_ascend,have_descend]=deal(zeros(n,m))
  for k=1:m
      v=have(:,k)
      [~,~,kk]=unique(v)
      have_ascend(:,k)=kk;
  end
  have_ascend(idx)=nan