disc
From spatstat v1.25-1
by Adrian Baddeley
Circular Window
Creates a circular window
Usage
disc(radius=1, centre=c(0,0), ..., mask=FALSE, npoly=128)
Arguments
- radius
- Radius of the circle.
- centre
- Coordinates of the centre of the circle.
- mask
- Logical flag controlling the type of approximation to a perfect circle. See Details.
- npoly
- Number of edges of the polygonal approximation,
if
mask=FALSE
. - ...
- Arguments passed to
as.mask
determining the pixel resolution, ifmask=TRUE
.
Details
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
.
Value
- An object of class
"owin"
(seeowin.object
) specifying a window.
Note
This function can also be used to generate regular polygons,
by setting npoly
to a small integer value. For example
npoly=5
generates a pentagon and npoly=13
a triskaidecagon.
See Also
Examples
# 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.owin(disc())/pi
area.owin(disc(mask=TRUE))/pi
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