These functions are the plot and persp methods
for objects of class "leverage.ppm".
Such objects are computed by the command leverage.ppm.
The plot method displays the leverage function
as a colour pixel image using plot.im,
and draws a single contour line at the mean leverage value
using contour.im.
Use the argument clipwin to restrict the plot to a subset
of the full data.
The persp method displays the leverage function as a surface
in perspective view, using persp.im.
References
Baddeley, A., Chang, Y.M. and Song, Y. (2013)
Leverage and influence diagnostics for spatial point process models.
Scandinavian Journal of Statistics40, 86--104.