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

Asked by Kobi
on 17 Sep 2014
Latest activity Edited by dpb
on 17 Sep 2014
Accepted Answer by dpb
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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1 Answer

Answer by dpb
on 17 Sep 2014
Edited by dpb
on 17 Sep 2014
 Accepted Answer

...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.

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