\renewcommand{\xunitdivisions}{2}
\renewcommand{\yunitdivisions}{3}

\begin{center}
\setlength{\unitlength}{1cm}%
\begin{Picture}(-4,-4)(4,4)
\cartesianaxes(-3.5,-3.5)(3.5,3.5)
\end{Picture}
\end{center}
