reach(x, ...)
"reach"(x, ..., epsilon=0)
"reach"(x, ...)
"reach"(x, ...)
"reach"(x, ..., epsilon)"ppm"), an interpoint interaction (object of class
"interact"), a fitted interpoint interaction (object of
class "fii") or a point process model for simulation
(object of class "rmhmodel").
NA if this cannot be
computed from the information given.
For example, the interaction range of a Strauss process
(see Strauss)
with parameters $beta,gamma,r$ is equal to
$r$, unless $gamma=1$ in which case the model is
Poisson and the interaction
range is $0$.
The interaction range of a Poisson process is zero.
The interaction range of the Ord threshold process
(see OrdThresh) is infinite, since two points may
interact at any distance apart.
The function reach(x) is generic, with methods
for the case where x is
"ppm", usually obtained from the model-fitting
function ppm);
"interact"), created by one of the functions
Poisson,
Strauss,
StraussHard,
MultiStrauss,
MultiStraussHard,
Softcore,
DiggleGratton,
Pairwise,
PairPiece,
Geyer,
LennardJones,
Saturated,
OrdThresh
or
Ord;
"fii") extracted from a fitted point process model
by the command fitin;
"rmhmodel"), usually obtained from rmhmodel.
When x is an "interact" object,
reach(x) returns the maximum possible interaction range
for any point process model with interaction structure given by x.
For example, reach(Strauss(0.2)) returns 0.2.
When x is a "ppm" object,
reach(x) returns the interaction range
for the point process model represented by x.
For example, a fitted Strauss process model
with parameters beta,gamma,r will return
either 0 or r, depending on whether the fitted
interaction parameter gamma is equal or not equal to 1.
For some point process models, such as the soft core process
(see Softcore), the interaction distance is
infinite, because the interaction terms are positive for all
pairs of points. A practical solution is to compute
the distance at which the interaction contribution
from a pair of points falls below a threshold epsilon,
on the scale of the log conditional intensity. This is done
by setting the argument epsilon to a positive value.
ppm,
Poisson,
Strauss,
StraussHard,
MultiStrauss,
MultiStraussHard,
Softcore,
DiggleGratton,
Pairwise,
PairPiece,
Geyer,
LennardJones,
Saturated,
OrdThresh,
Ord,
rmhmodel
reach(Poisson())
# returns 0
reach(Strauss(r=7))
# returns 7
fit <- ppm(swedishpines ~ 1, Strauss(r=7))
reach(fit)
# returns 7
reach(OrdThresh(42))
# returns Inf
reach(MultiStrauss(matrix(c(1,3,3,1),2,2)))
# returns 3
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