disc

0th

Percentile

Circular Window

Creates a circular window

Keywords
spatial, datagen
Usage
disc(radius=1, centre=c(0,0), ..., mask=FALSE, npoly=128, delta=NULL)
Arguments
centre
The centre of the circle.
Logical flag controlling the type of approximation to a perfect circle. See Details.
npoly
Number of edges of the polygonal approximation, if mask=FALSE. Incompatible with delta.
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.
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.

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.

Value

• An object of class "owin" (see owin.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.

ellipse, discs, owin.object, owin, as.mask

• disc
Examples
# unit disc
W <- disc()
# disc of radius 3 centred at x=10, y=5
W <- disc(3, c(10,5))
#
plot(disc())
area(disc(mask=TRUE))/pi