# 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.

- Keywords
- spatial

##### 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 1.6-2, License: GPL version 2 or newer*