# Ord

##### Generic Ord Interaction model

Creates an instance of an Ord-type interaction point process model which can then be fitted to point pattern data.

##### Usage

`Ord(pot, name)`

##### Arguments

- pot
An S language function giving the user-supplied interaction potential.

- name
Character string.

##### Details

Ord's point process model (Ord, 1977) is a Gibbs point process of infinite order. Each point \(x_i\) in the point pattern \(x\) contributes a factor \(g(a_i)\) where \(a_i = a(x_i, x)\) is the area of the tile associated with \(x_i\) in the Dirichlet tessellation of \(x\).

Ord (1977) proposed fitting this model to forestry data
when \(g(a)\) has a simple ``threshold'' form. That model is
implemented in our function `OrdThresh`

.
The present function `Ord`

implements the case of a
completely general Ord potential \(g(a)\)
specified as an S language function `pot`

.

This is experimental.

##### Value

An object of class `"interact"`

describing the interpoint interaction
structure of a point process.

##### References

Baddeley, A. and Turner, R. (2000)
Practical maximum pseudolikelihood for spatial point patterns.
*Australian and New Zealand Journal of Statistics*
**42**, 283--322.

Ord, J.K. (1977) Contribution to the discussion of Ripley (1977).

Ord, J.K. (1978)
How many trees in a forest?
*Mathematical Scientist* **3**, 23--33.

Ripley, B.D. (1977)
Modelling spatial patterns (with discussion).
*Journal of the Royal Statistical Society, Series B*,
**39**, 172 -- 212.

##### See Also

*Documentation reproduced from package spatstat, version 1.55-1, License: GPL (>= 2)*