
182 Spatial Point Patterns: Methodology and Applications with R
Two covariates
If there are two numerical covariates Z
1
(u),Z
2
(u) assumed to determine the intensity together, that
is
λ
(u) =
ρ
(Z
1
(u),Z
2
(u)), then similar techniques can be applied [37] to estimate the function
ρ
(z
1
,z
2
). These are implemen te d in the spatstat functio n rho2hat. For example
> with(bei.extra, rho2hat(bei, grad, elev))
would c ompute an estimate of the intensity of Beilschmiedia trees as a func tion jointly of the terrain
slope and terrain elevation.
6.6.4 D is tan ce map
One particularly important kind of spatial covariate is a distance function. The dataset copper is
described ...