Forming a block diagonal matrix of one certain matrix?

Question

diadalina 2020-1-13

0
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https://ww2.mathworks.cn/matlabcentral/answers/500105-forming-a-block-diagonal-matrix-of-one-certain-matrix

编辑： Matt J 2020-1-13

I have a matrix A which is m*n. I want to create a block tridiagonal matrices of size n*m whose diagonals elements are the matrix A.

B=eye(3);
C=ones(2);
S=ones(2);
for i=1:numel(A)
   A(i,i) =repmat(B,i,1)
    A(i,i+1)=repmat(C,i,1)
    A(i,i-1)=repmat(S,i,1)
end

can anyone help me to find the error

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diadalina 2020-1-13

mY matrix A shoud be like this

A=B C 0000

S B C 000

0 S B C 00

00 S B C 0

where B, C,S are matrices

Adam Danz 2020-1-13

If that's the example of A, then A cannot be a matrix. Is it a cell array or is the example misleading?

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Answer 1

Matt J 2020-1-13

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/500105-forming-a-block-diagonal-matrix-of-one-certain-matrix#answer_409952

编辑：Matt J 2020-1-13

在 MATLAB Online 中打开

using interpMatrix (Download)

S=1*ones(2);
B=2*ones(2);
C=3*ones(2);
copies=4; %number of repetitions
L=flip( {S,B,C, zeros(size(B))  } );
idx=full(interpMatrix([1,2,3],2,copies,1))+1;
A=cell2mat(L(idx))

A =
   2     3     3     0     0     0     0
   2     3     3     0     0     0     0
   1     2     2     3     3     0     0
   1     2     2     3     3     0     0
   0     1     1     2     2     3     3
   0     1     1     2     2     3     3
   0     0     0     1     1     2     2
   0     0     0     1     1     2     2