# rmhexpand

##### Specify Simulation Window or Expansion Rule

Specify a spatial domain in which point process simulations will be performed. Alternatively, specify a rule which will be used to determine the simulation window.

##### Usage

`rmhexpand(x = NULL, ..., area = NULL, length = NULL, distance = NULL)`

##### Arguments

- x
- Any kind of data determining the simulation window or the
expansion rule.
A window (object of class
`"owin"`

) specifying the simulation window, a numerical value specifying an expansion factor or expansion distance, a list conta - ...
- Ignored.
- area
- Area expansion factor. Incompatible with other arguments.
- length
- Length expansion factor. Incompatible with other arguments.
- distance
- Expansion distance (buffer width). Incompatible with other arguments.

##### Details

In the Metropolis-Hastings algorithm `rmh`

for simulating spatial point processes,
simulations are usually carried out on a spatial domain that is
larger than the original window of the point process model,
then subsequently clipped to the original window.

The command `rmhexpand`

can be used to specify the simulation window,
or to specify a rule which will later be used to determine the
simulation window from data.

The arguments are all incompatible: at most one of them should be given.

If the first argument `x`

is given, it may be any of the
following:

- a window (object of class
`"owin"`

) specifying the simulation window. - an object of class
`"rmhexpand"`

specifying the expansion rule. - a single numerical value, without attributes.
This will be interpreted as the value of the argument
`area`

. - either
`c(area=v)`

or`list(area=v)`

, where`v`

is a single numeric value. This will be interpreted as the value of the argument`area`

. - either
`c(length=v)`

or`list(length=v)`

, where`v`

is a single numeric value. This will be interpreted as the value of the argument`length`

. - either
`c(distance=v)`

or`list(distance=v)`

, where`v`

is a single numeric value. This will be interpreted as the value of the argument`distance`

. `NULL`

, meaning that the expansion rule is not yet determined.

If one of the arguments `area`

, `length`

or `distance`

is given, then the simulation window is determined from the original
data window as follows.
[object Object],[object Object],[object Object]

##### Value

- An object of class
`"rmhexpand"`

specifying the expansion rule. There is a`print`

method for this class.

##### Undetermined expansion

If `expand=NULL`

, this is interpreted to mean that the
expansion rule is `rmh`

.
If the model cannot be expanded (for example if the covariate data
in the model are not available on a larger domain) then expansion
will not occur. If the model can be expanded, then
if the point process model has a finite interaction range `r`

,
the default is `rmhexpand(distance=2*r)`

, and
otherwise `rmhexpand(area=2)`

.

##### See Also

`expand.owin`

to apply the rule to a window.

`will.expand`

to test whether expansion will occur.

`rmh`

, `rmhcontrol`

for background details.

##### Examples

```
rmhexpand()
rmhexpand(2)
rmhexpand(1)
rmhexpand(length=1.5)
rmhexpand(distance=0.1)
rmhexpand(letterR)
```

*Documentation reproduced from package spatstat, version 1.31-3, License: GPL (>= 2)*