Replace the values of a matrix by another values.

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]

Answer 1

[jonas]

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 =

     1     3     2
     2     3     1
     3     1     2

[Eranja Noopehewa]

I get an error undefined function 'maxk'

[jonas]

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

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

[jonas]

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.

Answer 2

[Star Strider]

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

[jonas]

+1

I figured there was a simpler solution...

[Star Strider]

Thank you.

This took a bit of experimenting to discover. It is probably robust, although I did not test it with other matrices.