construct a lower triangular matrix with smaller matrices

Hi all,

I'm looking for an algorithm to compute a lower triangular matrix made out of smaller, non-symmetric matrices, e.g. like:

A = [...
         1 2
         3 4
         5 6
        ];

B = [...
    0 0 0
    A 0 0
    A A 0
    A A A
    ];

Anyone can help? (Matlab 2015b btw)

[Jan]

What have you tried so far? Which problems occur? Some of the "0" are [3 x 2] matrices. Does this concern the zeros in the first row also?

Answer 1

[Jan]

A = [1 2; ...
     3 4; ...
     5 6];
B = tril(ones(4,3), -1);
R = kron(B, A)

R = 
  [0, 0,  0, 0,  0, 0; ...
   0, 0,  0, 0,  0, 0; ...
   0, 0,  0, 0,  0, 0; ...
   1, 2,  0, 0,  0, 0; ...
   3, 4,  0, 0,  0, 0; ...
   5, 6,  0, 0,  0, 0; ...
   1, 2,  1, 2,  0, 0; ...
   3, 4,  3, 4,  0, 0; ...
   5, 6,  5, 6,  0, 0; ...
   1, 2,  1, 2,  1, 2; ...
   3, 4,  3, 4,  3, 4; ...
   5, 6,  5, 6,  5, 6]