How to create a 2D diagonal matrix from a 3D matrix with a generic dimension? It could be with a loop structure.

%%3D matrix k

    n=3;
    k=zeros(n)
    for a=1:n
        for b=1:n
            for c=1:n
                k(b,c,a)=c;
            end
        end
    end

using blkdiag could be obtained, however for a generic number of matrices n, this doesn't work.

    u=blkdiag(k(:,:,1),k(:,:,2),k(:,:,3))

[Stephen23]

What is the expected output? Can you please provide a specific example with input and output arrays.

Answer 1

[KL]

Use a cell array and then something like,

c = arrayfun(@(x) k(:,:,x),1:n,'uni',0)
u = blkdiag(c{:})

u =

       1     2     3     0     0     0     0     0     0
       1     2     3     0     0     0     0     0     0
       1     2     3     0     0     0     0     0     0
       0     0     0     1     2     3     0     0     0
       0     0     0     1     2     3     0     0     0
       0     0     0     1     2     3     0     0     0
       0     0     0     0     0     0     1     2     3
       0     0     0     0     0     0     1     2     3
       0     0     0     0     0     0     1     2     3

Answer 2

[Matt J]

kcell=num2cell(k,[1,2]);

u=blkdiag(kcell{:});