creating a repeating diagonal matrix

I'm trying to create a diagonal matrix with the following sequence on the main diagonal line where v is the vector v=[4,1,0,1] to get the following matrix

[4 0 0 0 0 0 0

0 1 0 0 0 0 0

0 0 0 0 0 0 0

0 0 0 1 0 0 0

0 0 0 0 4 0 ...]

but I want it to repeat the same sequence over an over again for a 100 by 100 matrix how would I be able to do this?

[Muhammad Fiaz]

Can you do it?

Please I also need help..

Answer 1

[John D'Errico]

You want to repeat that sequence on the main diagonal?

v = [4 1 0 1];
A = diag(repmat(v,1,25));

That is, use repmat to replicate the sequece 25 times. Then use diag to create the associated diagonal matrix.

If you wanted the matrix to be a sparse matrix, you would use spdiags to form the matrix.

v = [4;1;0;1];
A = spdiags(repmat(v,25,1),0,100,100);

In the second form, I used spdiags. We can visualize the matrix as created using spy.

spy(A)

A dot is shown for all non-zero elements. You can even visualize those zero elements on the diagonal, because no dots were shown there.

[Josue Lujan]

yes i wanted to repeat the sequence on the main diaginal thank you!

[Muhammad Fiaz]

Can we repeat matrix is tri-diagnally?

e.g

[1 2 3 4]

I want to make it [1 2 0 0 0 0 ; 3 4 0 0 0 0 ; 0 0 1 2 0 0 ; 0 0 3 4 0 0 ; 0 0 0 0 1 2; 0 0 0 0 3 4]