find sorting index per row of a 2D matrix in MatLab and populate a new matrix

问题

I have a challenge to order my matrix. The provided functions like sortrows work in the opposite way...

Take this 2D matrix

M =
     40    45    68
     50    65    58
     60    55    48
     57    67    44    
                      ,

The objective is to find matrix O that indicates the sorting index (rank) per row, i.e.:

O =

     1     2     3
     1     3     2
     3     2     1
     2     3     1
                       .

So for the second row 50 is the smallest element (1), 65 the largest (3), and 58 is the second largest (2), therefore row vector [1 3 2].

回答1:

[~,sorted_inds] = sort(M,2);

will do.

回答2:

I think you're looking for the second output of the regular sort function:

[~,I] = sort(M,2)

This syntax supresses the actual sorted matrix Msorted, and returns the indices I such that

for j = 1:n, Msorted(j,:) = M(I(j,:),j); end

Type doc sort for more information.

来源：https://stackoverflow.com/questions/12112677/find-sorting-index-per-row-of-a-2d-matrix-in-matlab-and-populate-a-new-matrix