How to replicate an array diagonally for a given number of times?

I would like to replicate an array diagonally for a given number of times, so repmat command does not work in my case. I also tried blkdiag, but I have to write the name of the matrix 5 times if I want it to be recreated five times. I heard that it can be done with convolution from a friend of mine, yet my aim is to achieve the effect using basic commands.

Answer 1

[the cyclist]

Here is a very mundane way to do it. (I've assumed a square input, but it could easily be generalized.)

A = magic(5);
m = size(A,1);

N = 3;

AN = zeros(N*m);

for n=1:N
    range = (n-1)*m+1:n*m;
    AN(range,range) = A;
end

[Ongun]

Thanks it worked my friend suggested the following:

conv2(diag([upsample(ones(1,N-1),size(sub2D,1)),1]),sub2D);

with N being the number of replications, but yours are much easier to interpret.

Answer 2

[yeungor]

Alternatively, if you're not against "eval", you can use it to type out those repetitions n times.

a = rand(m,n);
N = 100;
A = eval(['blkdiag(a' repmat(',a', 1, N) ');']);

But the convolution way seems like less of a hack and it's still one line, it's a shame that it's black magic

[yeungor]

a = rand(m,n);
A = kron(eye(N), a)

Also works quite well