
Intensity 177
Figure 6.17. Perspective view o f rainforest terrain, shaded according to the estimated density of
Beilschmiedia trees per unit a rea of soil. Lighter shades represent higher predicted densities. Scale
on vertical axis is 6 times the scale on horizontal axes.
6.6 Investigating dependence of intensity on a covariate
6.6.1 Spatial covariates
Often we want to know how the intensity of points depends on the values of a covariate. For exam-
ple, for the Beilschmiedia data mentioned above, it is of interest to determine whether the trees prefer
steep or flat terrain, and wheth e r they prefer a particular altitu de. Other applications inclu d ...