Circular Window
Creates a circular window
disc(radius=1, centre=c(0,0), ..., mask=FALSE, npoly=128, delta=NULL)
radius |
Radius of the circle. |
centre |
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 |
delta |
Tolerance of polygonal approximation: the length of arc
that will be replaced by one edge of the polygon.
Incompatible with |
... |
Arguments passed to |
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.
An object of class "owin" (see owin.object)
specifying a window.
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.
Adrian Baddeley Adrian.Baddeley@curtin.edu.au
and Rolf Turner r.turner@auckland.ac.nz
# 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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