Order columns of matrix based on other matrix

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link 2021-1-28

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https://ww2.mathworks.cn/matlabcentral/answers/729708-order-columns-of-matrix-based-on-other-matrix

评论： link 2021-1-28

So in one matrix A I have the order of the elements

A =  3     1     3     1    3
     2     2     2     2    1   
     1     3     1     3    2  

and in the other matrix B are the actual values

B =  1     5     5     1    7
     2     6     7     2    4  
     4     8     8     6    5   

How can I use the columns of A to order the columns of B?

Result = 4     5     8     1    5
         2     6     7     2    7  
         1     8     5     6    4

So e.g. for the 5th column: 5 becomes the first value, 7 the first and 4 the third.

result(1,5) = B(A(1,5), 5); % A(1,5) = 3
result(2,5) = B(A(2,5), 5); % A(2,5) = 1
result(3,5) = B(A(3,5), 5); % A(3,5) = 2

Can I do this without using a loop?

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Answer 1

David Hill 2021-1-28

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Result=B(A+[0:3:12]);

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Adam Danz 2021-1-28

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Nice idea. To make it work for all matrix sizes,

Result=B(A+[0:size(A,1):numel(A(:,1:end-1))]);

link 2021-1-28

Thanks :) very neat

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Answer 2

Adam Danz 2021-1-28

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https://ww2.mathworks.cn/matlabcentral/answers/729708-order-columns-of-matrix-based-on-other-matrix#answer_608668

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Secret ingredient: sub2ind

A =  [3     1     3     1    3
     2     2     2     2    1   
     1     3     1     3    2 ]; 
B =  [1     5     5     1    7
     2     6     7     2    4  
     4     8     8     6    5 ];
 
 cols = (1:size(A,2)).*ones(size(A,1),1); 
 ind = sub2ind(size(B),A,cols); 
 
 Result = B(ind)
Result = 3×5
     4     5     8     1     5
     2     6     7     2     7
     1     8     5     6     4