Change the order of matrix

Question

NA 2020-4-1

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/514546-change-the-order-of-matrix

编辑： NA 2020-4-2

采纳的回答： Ameer Hamza

I want to change the order of B in accordance with Index.

Index means that 'row 2' in B should change to 'row 5' in New_B.

I wrote this code, but I don't know how to add remain elements in B to New_B.

B = [1 2; 1 4; 1 6; 1 8; 2 3; 2 7; 3 4; 3 6; 3 8; 4 6; 4 7; 6 7; 6 8; 7 8];
Index = [2,5; 4,1; 6,6; 8,2; 9,7; 10,3; 11,9; 12,4; 14,8]; 
New_B = zeros(size(B));
for i=1:length(Index)
    temp = Index(i,:);
    
        if temp(1)~=temp(2)
          New_B(temp(2),:)  = B(temp(1),:);
        end
     
end

result should be

New_B = [1,8; 3,6; 4,6; 6,7; 1,4; 1,2; 3,8; 7,8; 4,7; 1,6; 2,3; 2,7; 3,4; 3,4; 6,8]

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Guillaume 2020-4-1

Your index matrix tells us what happens to some of the rows of B. What about the others? What should be done about them?

Also, what if the instructions in Index conflict? e.g. Index sends 2 rows to the same destination?

NA 2020-4-1

''Given that the second column of Index only has indices going up to 9, how does your example output New_B contain 15 rows?''

B and New_B should be the same size.

''What about the others? What should be done about them?''

Orders of others are not impotant and coming after the arranged index.

''what if the instructions in Index conflict? e.g. Index sends 2 rows to the same destination?''

I have not encountered with mentioned case yet.

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Answer 1

Ameer Hamza 2020-4-1

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/514546-change-the-order-of-matrix#answer_423307

Try this:

B = [1 2; 1 4; 1 6; 1 8; 2 3; 2 7; 3 4; 3 6; 3 8; 4 6; 4 7; 6 7; 6 8; 7 8];
Index = [2,5; 4,1; 6,6; 8,2; 9,7; 10,3; 11,9; 12,4; 14,8];
B_temp = B;
B_temp(Index(:,1),:) = [];
B_new(Index(:,2),:) = B(Index(:,1),:);
B_new = [B_new; B_temp];

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Ameer Hamza 2020-4-2

Now the rule is a bit clear. Is this the required result?

B = [1 2; 2 3; 3 4; 4 5; 4 6; 6 8; 7 8];
Index = [3 2; 4 5; 5 7];
idx1 = Index(:,1);
idx2 = Index(:,2);
idx3 = setdiff(1:size(B,1), idx2)';
idx4 = setdiff(1:size(B,1), idx1)';
B_new(idx2, :) =  B(idx1,:);
B_new(idx3, :) = B(idx4,:);