Create a block diagonal, Toeplitz and triangular matrix given by n,B,C,A

Hello everyone,

Im trying to create an mn x mn matrix using m x m matrices. For example:

A = [1 2; 3 4]

B=[9 10; 11 12]

C = [ 5 6; 7 8]

n = 3

Should give me this answer: Attached image.

[Image Analyst]

I'm not going to delete John's question since he took his valuable time to donate to you. It would be rude to him to delete his post or the question that he answered.

You say this one is a duplicate question but if so, you deleted that one since this is the only question you've posted (and may well be the last one that anyone ever wants to answer). Please, as a courtesy to John, restore this one.

[Rik]

The original question had an image attached, but here is the text:

Create a block diagonal, Toeplitz and triangular matrix given by n,B,C,A

Hello everyone,

Im trying to create an mn x mn matrix using m x m matrices. For example:

A = [1 2; 3 4]

B=[9 10; 11 12]

C = [ 5 6; 7 8]

n = 3

Should give me this answer: Attached image.

[Rafael Nicolaou]

Im sorry i restored the question..

Thanks my fault.

[Rena Berman]

(Answers Dev) Restored edit

Answer 1

[John D'Errico]

The simplest answer is to use my blktridiag utility from the file exchange.

full(blktridiag(A,C,B,3))
ans =
1     2     9    10     0     0
3     4    11    12     0     0
5     6     1     2     9    10
7     8     3     4    11    12
0     0     5     6     1     2
0     0     7     8     3     4

By default, it produces a sparse matrix. Since you did not ask for that, I put a call to full around it.

Of course, if this is homework, then my answer is useless. If it is not, then my answer is the perfect solution. Find blktridiag on the File Exchange at this link:

https://www.mathworks.com/matlabcentral/fileexchange/10603-block-tri-diagonal-matrices?s_tid=srchtitle

Could you solve it using blkdiag? Well, yes, if this is your homework, with some effort. In that case, you you create the main diagonal of matrices from A? How might you do that? Perhaps that is a sufficient hint to get you started, IF this is your homework. Better is to just use code designed to solve your problem, efficient, already written and debugged.