Randomly create lower and upper of matrix separately.

I would like to create a randomly lower triangle of the matrix, and then create an upper triangle of matrix separately. After that I want to compound both of these in one matrix. More deeply, I want to control each cell in both half matrix.

[Azzi Abdelmalek]

can you give more details? illustrate with an example

[John D'Errico]

What do you mean to "control each cell"?

You can always access any element of a matrix.

[Abe]

I meant above, I want to create a random number in each cell of the lower - matrix, and then separately do the same with upper-matrix. The conclusion will be I have 1/2 of matrix (Upper matrix) generated alone, and the other half (lower matrix) generated lonely too. So when add the 2 halves I see one matrix with keeping the same generated numbers. I hope now it's clear. Thank you for asking.

Answer 1

[Shoaibur Rahman]

l = tril(rand(m,n),-1); % lower triangle
u = triu(rand(m,n),1); % upper triangle
d = diag(rand(1,m),0); % diagonal elements
A = l+u+d % final matrix, combined all

If you don't want to generate the diagonal elements separately, then replace either -1 in lower triangle or 1 in upper triangle by 0, and then A = l+u

[Abe]

Thanks a lot, it's working with me right now