acces indexes of Multidimensional arrays while using index of elements in a vector?

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Kobi 2014-9-17

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https://ww2.mathworks.cn/matlabcentral/answers/155183-acces-indexes-of-multidimensional-arrays-while-using-index-of-elements-in-a-vector

编辑： dpb 2014-9-17

采纳的回答： dpb

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i have a vector called L the vector contain indexes

also i need to use those indexes while writing the totl matrix MAT(L) into a multidimantional array by doing this:

all this is inside a loop

for k=1:anynumber
  MAT(:,:,k)

i found that the script doesn't write at all to the destination matrics it only write to the index (:,:,1) and the rest are zeros.

H(:,:,length(frequencies))=zeros(max(rx_pos),max(tx_pos));
LinInd=sub2ind(size(H(:,:,length(frequencies))),rx_pos,tx_pos);
H(LinInd)=Escat;
H(:,:,k)=H(LinInd);

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Answer 1

dpb 2014-9-17

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https://ww2.mathworks.cn/matlabcentral/answers/155183-acces-indexes-of-multidimensional-arrays-while-using-index-of-elements-in-a-vector#answer_152009

编辑：dpb 2014-9-17

在 MATLAB Online 中打开

...the script ... only write[s] to the index (:,:,1)

Yes, because your index-computing expression only addresses a plane in the 3D array, not the whole array. In the expression size(H(:,:,length(frequencies))), the answer is the x,y dimension of a plane so you compute the linear address in the plane, not in the array.

Use

LinInd=sub2ind(size(H),rx_pos,tx_pos,k);

instead for each plane k and then

H(LinInd)=Escat;

where

length(Escat)==length(LinEnd)

You don't need (or want) the subsequent H(:,:,k) assignment at all--that's what the linear addresses will take care of when you convert them to 3D indexing.