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.
rmhexpand(x = NULL, ..., area = NULL, length = NULL, distance = NULL)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 containing
one numerical value, an object of class "rmhexpand",
or NULL.
Ignored.
Area expansion factor. Incompatible with other arguments.
Length expansion factor. Incompatible with other arguments.
Expansion distance (buffer width). Incompatible with other arguments.
An object of class "rmhexpand" specifying the
expansion rule. There is a print method for this class.
If expand=NULL, this is interpreted to mean that the
expansion rule is “not yet decided”. Expansion will be decided
later, by the simulation algorithm 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).
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.
The bounding box of the original data window will be extracted,
and the simulation window will be a scalar dilation of this rectangle.
The argument area should be a numerical value, greater than
or equal to 1. It specifies the area expansion factor, i.e. the ratio
of the area of the simulation window to the area of the
original point process window's bounding box.
The bounding box of the original data window will be extracted,
and the simulation window will be a scalar dilation of this rectangle.
The argument length should be a numerical value, greater than
or equal to 1. It specifies the length expansion factor, i.e. the ratio
of the width (height) of the simulation window to the width
(height) of the original point process window's bounding box.
The argument distance should be a numerical value, greater than
or equal to 0. It specifies the width of a buffer region around the
original data window.
If the original data window is a rectangle, then this window
is extended by a margin of width equal to distance
around all sides of the original rectangle. The result is a
rectangle.
If the original data window is not a rectangle, then
morphological dilation is applied using
dilation.owin
so that a margin or buffer of width equal to distance
is created around all sides of the original window. The result
is a non-rectangular window, typically of a different shape.
expand.owin to apply the rule to a window.
will.expand to test whether expansion will occur.
rmh, rmhcontrol for background details.
# NOT RUN {
rmhexpand()
rmhexpand(2)
rmhexpand(1)
rmhexpand(length=1.5)
rmhexpand(distance=0.1)
rmhexpand(letterR)
# }
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