indexing diagonals out of a 3d matrix
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I thought this would be fairly simple. I thought the diag function should be able to do this task. I have a 14x14x1045 matrix Ht, t=1,...,1045 simbolizes the number of observations. I merely want to extract the main daigonals of Ht for all t and store them in a new 3d matrix Dt which is also 14x14x1045 which contains the diagonal elements of every Ht and zeros in all other positions. However, when using the function diag(Ht) I get the following error: Error using diag First input must be 2D.
Is there a function that works like diag but for 3d matrices? I have no experience programing any functions. Could someone please provide a simple loop to make a function that fulfills this task in case no such function exists already?
I´m sorry if this question is too trivial, but I haven´t been able to find a specific answer and I seem not to be able to program such a function with my expertise level...
Thanks a lot for your help!
采纳的回答
D=bsxfun(@times, eye(size(H(:,:,1))), H)
更多回答（2 个）
A = rand(14,14,1045);
B = A(logical(repmat(eye(size(A(:,:,1))),[1 1 size(A,3)])))
Kiran Sagar
2013-7-9
I think this would work elegantly. But I don't know if this would take up alot of time/memory for your purposes.
for i=1:1045
Dt(:,:,i)=diag(diag(Ht(:,:,i)));
end
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2013-7-9
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