Section: Sparse Matrix Support
y = sparse(x).
The second form creates a sparse matrix containing all zeros
that is of the specified size (the sparse equivalent of
zeros).
y = sparse(m,n)
where m and n are integers.  Just like the zeros function,
the sparse matrix returned is of type float.  The third form 
constructs a sparse matrix from the IJV syntax.  It has two forms.  The
first version autosizes the sparse matrix 
y = sparse(i,j,v)
while the second version uses an explicit size specification
y = sparse(i,j,v,m,n)