# Pairwise

##### Generic Pairwise Interaction model

Creates an instance of a pairwise interaction point process model which can then be fitted to point pattern data.

- Keywords
- spatial

##### Usage

```
Pairwise(pot, name)
Pairwise(pot, name, par, parnames)
```

##### Arguments

- pot
- An S language function giving the user-supplied pairwise interaction potential.
- name
- Character string.
- par
- List of numerical values for irregular parameters
- parnames
- Vector of names of irregular parameters

##### Details

Advanced use only.
This code constructs a member of the
pairwise interaction family `pairwise.family`

with arbitrary pairwise interaction potential given by
the user.

The function `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 `pot`

should be a vector of the same type as `par`

giving those parameter values.

##### Value

- An object of class
`"interact"`

describing the interpoint interaction structure of a point process.

##### synopsis

Pairwise(pot, name, par, parnames, printfun)

##### See Also

##### Examples

```
#This is the same as StraussHard(r=0.7,h=0.2)
strpot <- function(t,par) {
r <- par$r
h <- par$h
value <- (t <= r)
value[t < h] <- -Inf
value
}
mySH <- Pairwise(strpot, "StraussHard", list(r=0.7,h=0.2),
c("interaction distance r", "hard core distance c"))
data(cells)
ppm(cells, ~ 1, mySH)
```

*Documentation reproduced from package spatstat, version 1.5-5, License: GPL version 2 or newer*