3d Matrix - Extract Subarray and Multiply by Conjugate Transpose without Forloops
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I have a 3d matrix A(i,j,k) of size [1:100,1:10000,1:989]. On the kth index I want to extract the 989 elements into a vector u and form the product u*ctranspose(u), for each of the
indices.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1118700/image.png)
Using a double for loop, which is not something one should do in Matlab,
% this is an evil double for loop - I want to avoid doing this.
for ii=1:100
for jj=1:10000
u=squeeze(A(ii,jj,:));
% somehow compute and store uu in a vectorized way, but how?
uu=u*ctranspose(u); % note that uu is a 989x989 matrix, not a vector.
end %ii
end %jj
This would be really slow. Is there a vectorized way to the above, so I am not doing a double for loop?
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