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Rengin
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Sub-Matrices in a bigger matrix

Asked by Rengin
on 19 Jul 2019
Latest activity Edited by Jan
on 19 Jul 2019
Dear Users,
Imagine that I have 4 square matrices such as A11, B11, C11 and D22.
I want to insert them as diagonal elements of a bigger matrix (please see the pic on the attchments).
However, I don't know the size of the bigger matrix. I will find it out when I insert all sub-matrices. Is there any easy way to do it?
Thanks in advance!

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2 Answers

Answer by madhan ravi
on 19 Jul 2019
 Accepted Answer

blkdiag(A11, B11, C11, D22)

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Rengin
on 19 Jul 2019
Thank you for the answer! Do you also know how to implement other sub-matrices in this big matrix (please see e.g. A12, A13, B21...etc. in the figure on the attcahments) ?
madhan ravi
on 19 Jul 2019
m = size(A11,1);
Wanted = blkdiag(A11, B11, C22, D22);
Wanted(1:m,m+1:end) = [A12,A13,A14];
Wanted(m+1:m*2,1:m) = B21

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Answer by Andrei Bobrov
on 19 Jul 2019

For matrices with the same size. Let [m,n] - size of each matrix, q - number of matrices in the vertical of a large matrix:
M = cat(3,A11,B21,..,A12,B11,..,A13,..,C11,..D22);% A11, B21 and etc - your small matrices
out = reshape(permute(reshape(M,m,n,q,[]),[1,3,2,4]),q*m,[]);

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