I'm trying to plot contour lines of a two variable function. I found this example here:
\begin{tikzpicture}
\begin{axis}[view={0}{90}]
\addplot3[contour gnuplot={
labels over line,number=9}]
{x*y};
\end{axis}
\end{tikzpicture}
But I get the following error:
! Package pgfplots Error: sorry, plot file{plots_contourtmp0.table} could not be opened.
What is going on?