Replace the values of a matrix by another values.

Question

Eranja Noopehewa 2018-7-31

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https://ww2.mathworks.cn/matlabcentral/answers/412943-replace-the-values-of-a-matrix-by-another-values

编辑： jonas 2018-7-31

i have a 3*3 matrix like [750 360 500 ; 550 520 780 ; 150 350 270] I want to replace these values in the matrix by comparing each row from the largest to small. (i.e largest =1 ,second largest=2 and smallest =3 ). Finally is should get a matrix like [1 3 2 ;2 3 1 ;3 1 2]

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Answer 1

jonas 2018-7-31

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https://ww2.mathworks.cn/matlabcentral/answers/412943-replace-the-values-of-a-matrix-by-another-values#answer_331087

编辑：jonas 2018-7-31

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I have a feeling there is an obvious simple solution to this problem. However, you can use this for now :)

A = [750 360 500 ; 550 520 780 ; 150 350 270];
[~,ind] = maxk(A,3,2);
out = nan(size(A));
for i = 1:3
  out(sub2ind(size(A),[1:length(A)]',ind(:,i))) = i;
end

out =

   3     2
   3     1
   1     2

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jonas 2018-7-31

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Okay, it's because you are using an older release of MATLAB. Replace that line by this:

[~,ind]=sort(A,2,'descend')

jonas 2018-7-31

编辑：jonas 2018-7-31

I'm happy it helped, but to be honest you should accept the other answer. I was going to delete this one but wanted to wait until you were finished with testing it. This one is slower and probably not as robust. It is also not generalized, and currently only works for 3x3 matrices.

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Answer 2

Star Strider 2018-7-31

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https://ww2.mathworks.cn/matlabcentral/answers/412943-replace-the-values-of-a-matrix-by-another-values#answer_331091

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This appears to do what you want:

A = [750 360 500 ; 550 520 780 ; 150 350 270];
[~,Idx] = sort(A,2,'descend');                          % Sort Matrix Row-Wise, Descending, Return Indices
[~,Out] = sort(Idx,2)                                   % Sort Indices Row-Wise, Ascending, Return Indices To Get Output
Out =
     1     3     2
     2     3     1
     3     1     2