Assign values of array to indices of another array

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Georg Bauer ，2022-8-16

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https://ww2.mathworks.cn/matlabcentral/answers/1779960-assign-values-of-array-to-indices-of-another-array

评论： Georg Bauer ，2022-8-16

Hello!

I'm not really sure how to word my question (hence the confusing title!). I do have to arrays:

A = [1,2;3,4];
B = [11;22;33;44];

Now I would like to arrange the elements of B in the order of array A. The output should then be like that:

B(A) = [11,22;33,44]

But now I wanna leave some places of the array 0. So at position A(1,1) where there is a zero shouldn't be a vallue of B asignd to (B(1,1) therefore should stay 0 as well).

A = [0,2;3;4];
B(A) = [0,22;33;44]

Thank you!

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James Tursa 2022-8-16

Need more details. Is the indexing in A always in that order, except for some of the spots might be 0? Or could the indexing be in a different order such as A = [2,0;4,3]?

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Answer 1

Chunru 2022-8-16

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https://ww2.mathworks.cn/matlabcentral/answers/1779960-assign-values-of-array-to-indices-of-another-array#answer_1027065

A = [1; 2; 3; 4];
B = [11; 22; 33; 44];
B(A) 
ans = 4×1
    11
    22
    33
    44
A = [0; 2; 3; 4];
C = zeros(size(A));
C(A>0) = B(A(A>0))
C = 4×1
     0
    22
    33
    44