Make a spatial region composed of discs with given centres and radii.
discs(centres, radii = marks(centres)/2, …,
separate = FALSE, mask = FALSE, trim = TRUE,
delta = NULL, npoly=NULL)Point pattern giving the locations of centres for the discs.
Vector of radii for each disc, or a single number giving a common
radius.
(Notice that the default assumes that the marks of X are
diameters.)
Optional arguments passed to as.mask to determine
the pixel resolution, if mask=TRUE.
Logical. If TRUE, the result is a list
containing each disc as a separate entry.
If FALSE (the default), the result is a window
obtained by forming the union of the discs.
Logical. If TRUE, the result is a binary mask window.
If FALSE, the result is a polygonal window.
Applies only when separate=FALSE.
Logical value indicating whether to restrict the result
to the original window of the centres.
Applies only when separate=FALSE.
Argument passed to disc to determine the
tolerance for the polygonal approximation of each disc.
Applies only when mask=FALSE.
Incompatible with npoly.
Argument passed to disc to determine the
number of edges in the polygonal approximation of each disc.
Applies only when mask=FALSE.
Incompatible with delta.
If separate=FALSE, a window (object of class "owin").
If separate=TRUE, a list of windows.
This command is typically applied to a marked point pattern
dataset X in which the marks represent the sizes of objects.
The result is a spatial region representing the space occupied by
the objects.
If the marks of X represent the diameters of circular objects,
then the result of discs(X)
is a spatial region constructed by taking discs, of the specified
diameters, centred at the points of X, and forming the union
of these discs. If the marks of X represent the areas of
objects, one could take discs(X, sqrt(marks(X)/pi))
to produce discs of equivalent area.
A fast algorithm is used to compute the result as a binary mask, when
mask=TRUE. This option is recommended unless polygons are
really necessary.
If mask=FALSE, the discs will be constructed as polygons
by the function disc. To avoid computational problems,
by default, the discs will all be constructed using
the same physical tolerance value delta
passed to disc. The default is such that the smallest
disc will be approximated by a 16-sided polygon.
(The argument npoly should not normally be used, to avoid
computational problems arising with small radii.)
# NOT RUN {
plot(discs(anemones, mask=TRUE, eps=0.5))
# }
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