Question

I have to create a matlab matrix that is much bigger that my phisical memory, and i want to take advantage of the sparsity.

This matrix is really really sparse [say N elements in an NxN matrix], and my ram is enought for this. I create the matrix in this way:

A=sparse(zeros(N));

but it goes out of memory.
Do you know the right way to create this matrix?

Answer 1

zeros(N) is creating an NxN matrix, which is not sparse, hence you are running out of memory. Your code is equivalent to

temp = zeros(N)
A = sparse(temp)

Just do sparse(N,N).