Plot a two-dimensional fit-statistic contour plot of the last steppar run.
XSPEC> plot contour [<min. fit stat.> [<num. levels> [<levels>]]]
where <min. fit stat.> is the minimum fit statistic relative
to which the delta fit statistic is calculated, <num. levels>
is the number of contour levels to use and <levels> :=
<level1> ... <levelN> are the contour levels in the delta fit statistic.
contour will plot the fit statistic grid calculated by the last steppar command (which should have gridded on two parameters). A small plus sign (+) will be drawn on the plot at the parameter values corresponding to the minimum found by the most recent fit.