R: The Multitype Hard Core Point Process Model

MultiHard {spatstat.core} | R Documentation

## The Multitype Hard Core Point Process Model

### Description

Creates an instance of the multitype hard core point process model which can then be fitted to point pattern data.

### Usage

      MultiHard(hradii, types=NULL)

### Arguments

`hradii` | Matrix of hard core radii
`types` | Optional; vector of all possible types (i.e. the possible levels of the `marks` variable in the data)

### Details

This is a multitype version of the hard core process. A pair of points of types i and j must not lie closer than h[i,j] units apart.

The argument `types` need not be specified in normal use. It will be determined automatically from the point pattern data set to which the MultiStrauss interaction is applied, when the user calls `ppm`. However, the user should be confident that the ordering of types in the dataset corresponds to the ordering of rows and columns in the matrix `hradii`.

The matrix `hradii` must be symmetric, with entries which are either positive numbers or `NA`. A value of `NA` indicates that no distance constraint should be applied for this combination of types.

Note that only the hardcore radii are specified in `MultiHard`. The canonical parameters log(beta[j]) are estimated by `ppm()`, not fixed in `MultiHard()`.

### Value

An object of class `"interact"` describing the interpoint interaction structure of the multitype hard core process with hard core radii hradii[i,j].

### Warnings

In order that `ppm` can fit the multitype hard core model correctly to a point pattern `X`, this pattern must be marked, with `markformat` equal to `vector` and the mark vector `marks(X)` must be a factor. If the argument `types` is specified it is interpreted as a set of factor levels and this set must equal `levels(marks(X))`.

### Changed Syntax

Before spatstat version `1.37-0`, the syntax of this function was different: `MultiHard(types=NULL, hradii)`. The new code attempts to handle the old syntax as well.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au, Rolf Turner r.turner@auckland.ac.nz and Ege Rubak rubak@math.aau.dk.

### See Also

`ppm`, `pairwise.family`, `ppm.object`, `MultiStrauss`, `MultiStraussHard`, `Strauss`.

See `ragsMultiHard` and `rmh` for simulation.

### Examples

       h <- matrix(c(1,2,2,1), nrow=2,ncol=2)

       # prints a sensible description of itself
       MultiHard(h)

       # Fit the stationary multitype hardcore process to `amacrine'
       # with hard core operating only between cells of the same type.
       h <- 0.02 * matrix(c(1, NA, NA, 1), nrow=2,ncol=2)
       ppm(amacrine ~1, MultiHard(h))

[Package spatstat.core version 2.4-4 Index]