error "Out of range subscript"??

Question

Sahar abdalah 2015-7-6

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回答： Walter Roberson 2015-7-6

I have two matrix: decision.mat and order.mat. the order matrix contains labels and the decision matrix contains indices of element and I want to obtain a matrix result that corresponding to the values in order according to the indices of the matrix decision. there is an example :

    order=[1;25;6;5;2];
    decision=[1;2;5;4;3];
    resultat=[1;25;2;5;6];

I use this code to obtain but I got this error :

 [n,m]=size(decision);
resultat=reshape( order(sub2ind([n,m],(1:n)'*ones(1,m),decision)),n,m);
Error using sub2ind (line 52)
 Out of range subscript.
   Error in ex2 (line 7)
   resultat=reshape( order(sub2ind([n,m],(1:n)'*ones(1,m),decision)),n,m);

please help me to solve this problem and thanks in advance.

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Answer 1

Walter Roberson 2015-7-6

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[n,m] = size(decision) is going to give n = 5, m = 1. ones(m,1) is then going to be the scalar 1. (1:n)' is going to be [1;2;3;4;5] and * 1 that is going to give the same. So now you are trying to sub2ind([5,1], [1;2;3;4;5], [1;2;5;4;3]) . That would require that [1,1], [2, 2], [3, 5], [4, 4], [5, 3] be valid subscripts of a 5 x 1 vector. Only the first of those is valid.

I do not know what you are trying to do there. I suspect you are trying to permute order by rows. If so then just

order(decision,:)

would be enough.