# OrdThresh

##### Ord's Interaction model

Creates an instance of Ord's point process model which can then be fitted to point pattern data.

##### Usage

`OrdThresh(r)`

##### Arguments

- r
- Positive number giving the threshold value for Ord's model.

##### 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 $x$. The function $g$ is simply $g(a) = 1$ if $a \ge r$ and $g(a) = \gamma < 1$ if $a < r$, where $r$ is called the threshold value.

This function creates an instance of Ord's model with a given
value of $r$. It can then be fitted to point process data
using `ppm`

.

##### 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 1.9-3, License: GPL version 2 or newer*