how to find the indices after sorting columns of a matrix

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Danish Nasir 2022-5-31

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回答： SALAH ALRABEEI 2022-5-31

Suppose i have 4x4 matrix A with different integers. I sort each column of the matrix i.e. B= sort (A,'ascend'). Now i want matrix C which should show changed indices of matrix A after sorting.

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Answer 1

SALAH ALRABEEI 2022-5-31

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If I got you correctly, I think you want you want this

clear
A = magic(4)
A = 4×4
    16     2     3    13
     5    11    10     8
     9     7     6    12
     4    14    15     1
[n,m]=size(A)
n = 4
m = 4
[As,Cur_ind]=sort(A,'ascend')
As = 4×4
     4     2     3     1
     5     7     6     8
     9    11    10    12
    16    14    15    13
Cur_ind = 4×4
     4     1     1     4
     2     3     3     2
     3     2     2     3
     1     4     4     1
Org_ind = reshape(1:n*m,n,m)
Org_ind = 4×4
     1     5     9    13
     2     6    10    14
     3     7    11    15
     4     8    12    16
bb=[1:n].*ones(n,m)
bb = 4×4
     1     2     3     4
     1     2     3     4
     1     2     3     4
     1     2     3     4
C = reshape(diag(Org_ind(Cur_ind,bb)),n,m)
C = 4×4
     4     5     9    16
     2     7    11    14
     3     6    10    15
     1     8    12    13