\name{Pairwise}
\alias{Pairwise}
\title{Generic Pairwise Interaction model}
\description{
Creates an instance of a pairwise interaction point process model
which can then be fitted to point pattern data.
}
\usage{
Pairwise(pot, name, par, parnames, printfun)
}
\arguments{
\item{pot}{An S language function giving the user-supplied
pairwise interaction potential.}
\item{name}{Character string.}
\item{par}{List of numerical values for irregular parameters}
\item{parnames}{Vector of names of irregular parameters}
\item{printfun}{Do not specify this argument: for internal use only.}
}
\value{
An object of class \code{"interact"}
describing the interpoint interaction
structure of a point process.
}
\details{
Advanced use only.
This code constructs a member of the
pairwise interaction family \code{\link{pairwise.family}}
with arbitrary pairwise interaction potential given by
the user.
The function \code{pot} must take as its first argument
a matrix of interpoint distances, and evaluate the
potential for each of these distances. The result must be
either a matrix with the same dimensions as its input,
or an array with its first two dimensions the same as its input
(the latter case corresponds to a vector-valued potential).
If irregular parameters are present, then the second argument
to \code{pot} should be a vector of the same type as \code{par}
giving those parameter values.
}
\seealso{
\code{\link{ppm}},
\code{\link{pairwise.family}},
\code{\link{ppm.object}}
}
\examples{
#This is the same as StraussHard(r=0.7,h=0.05)
strpot <- function(d,par) {
r <- par$r
h <- par$h
value <- (d <= r)
value[d < h] <- -Inf
value
}
mySH <- Pairwise(strpot, "StraussHard", list(r=0.7,h=0.05),
c("interaction distance r", "hard core distance c"))
data(cells)
ppm(cells, ~ 1, mySH, correction="isotropic")
}
\author{Adrian Baddeley
\email{adrian@maths.uwa.edu.au}
\url{http://www.maths.uwa.edu.au/~adrian/}
and Rolf Turner
\email{r.turner@auckland.ac.nz}
}
\keyword{spatial}
\keyword{models}