[pstricks] Double arrow and single arrow needed.

[David Arnold]

All,

This doesn't quite so what I want.

\documentclass[11pt]{article}
\usepackage{amsmath}
\usepackage{graphicx}
\usepackage[dvipsnames]{pstricks}
\usepackage{pstricks-add,auto-pst-pdf}

\PreviewEnvironment{psgraph}

\begin{document}

\begin{center}
\begin{psgraph}{<->}(0,0)(0,-3)(\psPiTwo,3){0.6\linewidth}{2in}
\end{psgraph}
\end{center}

\end{document}

I have a double arrow for both axes, but I want the double arrow for  
the y-axis, but only a right pointing arrow for the x-axis.

Any suggestions?

Thanks.

D.