SPARSE SPARSE Construct a Sparse Matrix

Usage

Creates a sparse matrix using one of several formats.  The 
first creates a sparse matrix from a full matrix

   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)

