Create a lower triangular matrix from a given vector

Question

My problem is the following: I have a vector as

[3,4,5,6,7]

I want to create a matrix as

3 0 0 0 0   
3 4 0 0 0   
3 4 5 0 0   
3 4 5 6 0   
3 4 5 6 7 

However, I don't want to use for loops because of the problem of size that I will eventually get. I was thinking about using flipud, fliprl, hankel and toeplitz functions but cannot find a solution.

Answer 1

Try this:

x = [3,4,5,6,7]
tril(ones(length(x),1)*x)

ans =

 3     0     0     0     0
 3     4     0     0     0
 3     4     5     0     0
 3     4     5     6     0
 3     4     5     6     7

Answer 2

If A is your vector, you can do

M=repmat(A, length(A), 1) .* tril(ones(length(A),length(A)),0)