Creates a circular window
disc(radius=1, centre=c(0,0), …, mask=FALSE, npoly=128, delta=NULL)Radius of the circle.
The centre of the circle.
Logical flag controlling the type of approximation to a perfect circle. See Details.
Number of edges of the polygonal approximation,
if mask=FALSE. Incompatible with delta.
Tolerance of polygonal approximation: the length of arc
that will be replaced by one edge of the polygon.
Incompatible with npoly.
Arguments passed to as.mask determining the
pixel resolution, if mask=TRUE.
An object of class "owin" (see owin.object)
specifying a window.
This command creates a window object representing a disc, with the given radius and centre.
By default, the circle is
approximated by a polygon with npoly edges.
If mask=TRUE, then the disc is approximated by a binary pixel
mask. The resolution of the mask is controlled by
the arguments … which are passed to as.mask.
The argument radius must be a single positive number.
The argument centre specifies the disc centre: it can be either
a numeric vector of length 2 giving the coordinates,
or a list(x,y) giving the coordinates of exactly one point, or a
point pattern (object of class "ppp") containing exactly one point.
# NOT RUN {
# unit disc
W <- disc()
# disc of radius 3 centred at x=10, y=5
W <- disc(3, c(10,5))
#
plot(disc())
plot(disc(mask=TRUE))
# nice smooth circle
plot(disc(npoly=256))
# how to control the resolution of the mask
plot(disc(mask=TRUE, dimyx=256))
# check accuracy of approximation
area(disc())/pi
area(disc(mask=TRUE))/pi
# }
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