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how to solve diagonal matrix of each page of a 3D vector ? pagediag?

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Jiawen Luo
Jiawen Luo 2023-6-28
评论： Bruno Luong 2023-8-10
There is a 3D vector A, it has 100 pages, each page is a 1×20 vector. I want to solve diagonal matrix of each 1×20 vector.
A=rand(1,20,100);
for k=1:100
B(:,:,k)=diag(A(:,:,k));
end
B is a 20×20×100 matrix.
I'm trying to vectorize this expression, is there a matlab function maybe called 'pagediag' that can solve B=pagediag(A) ?
  1 个评论
Matt J
Matt J 2023-6-28
I am concerned about why you think you need a pagediag.If you plan to use it in conjunction with pagemtimes to scale the rows or columns of a stack of matrices, it's the wrong approach.

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回答（3 个）

Matt J
Matt J 2023-6-28
编辑：Matt J 2023-6-28
Ran in:
A=rand(1,4,3)
A =
A(:,:,1) = 0.0986 0.2790 0.2407 0.2268 A(:,:,2) = 0.4894 0.0108 0.5699 0.2451 A(:,:,3) = 0.5105 0.6127 0.1543 0.3238
[~,n,p]=size(A);
B=zeros(n^2,p);
B(1:n+1:end,:)=reshape(A,n,p);
B=reshape(B,n,n,p)
B =
B(:,:,1) = 0.0986 0 0 0 0 0.2790 0 0 0 0 0.2407 0 0 0 0 0.2268 B(:,:,2) = 0.4894 0 0 0 0 0.0108 0 0 0 0 0.5699 0 0 0 0 0.2451 B(:,:,3) = 0.5105 0 0 0 0 0.6127 0 0 0 0 0.1543 0 0 0 0 0.3238
Bruno Luong
Bruno Luong 2023-6-28
[~,n,p] = size(A);
[J,K] = ndgrid(1:n,1:p);
B = accumarray([J(:) J(:) K(:)], A(:), [n,n,p]);
shobun
shobun 2023-8-10
A.*eye(20)
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shobun
shobun 2023-8-10
Ran in:
Thanks!
for column vectors
A=rand(3,1,5)
A =
A(:,:,1) = 0.2270 0.3032 0.1406 A(:,:,2) = 0.7674 0.6613 0.2126 A(:,:,3) = 0.3058 0.1203 0.2630 A(:,:,4) = 0.9825 0.3091 0.3544 A(:,:,5) = 0.7992 0.5751 0.6762
diagA=eye(3).*A
diagA =
diagA(:,:,1) = 0.2270 0 0 0 0.3032 0 0 0 0.1406 diagA(:,:,2) = 0.7674 0 0 0 0.6613 0 0 0 0.2126 diagA(:,:,3) = 0.3058 0 0 0 0.1203 0 0 0 0.2630 diagA(:,:,4) = 0.9825 0 0 0 0.3091 0 0 0 0.3544 diagA(:,:,5) = 0.7992 0 0 0 0.5751 0 0 0 0.6762

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