\section{SPARSE Construct a Sparse Matrix}

\subsection{Usage}

Creates a sparse matrix using one of several formats.  The 
first creates a sparse matrix from a full matrix
\begin{verbatim}
   y = sparse(x).
\end{verbatim}
The second form creates a sparse matrix containing all zeros
that is of the specified size (the sparse equivalent of
\verb|zeros|).
\begin{verbatim}
   y = sparse(m,n)
\end{verbatim}
where \verb|m| and \verb|n| are integers.  Just like the \verb|zeros| function,
the sparse matrix returned is of type \verb|float|.  The third form 
constructs a sparse matrix from the IJV syntax.  It has two forms.  The
first version autosizes the sparse matrix 
\begin{verbatim}
   y = sparse(i,j,v)
\end{verbatim}
while the second version uses an explicit size specification
\begin{verbatim}
   y = sparse(i,j,v,m,n)
\end{verbatim}
