spatstat.geom (version 3.2-5)

disc: Circular Window

Description

Creates a circular window

Usage

disc(radius=1, centre=c(0,0), ...,
      mask=FALSE, npoly=128, delta=NULL,
      metric=NULL)

Value

An object of class "owin" (see owin.object) specifying a window.

Arguments

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 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.

metric

Optional. A distance metric (object of class "metric"). The disc with respect to this metric will be computed.

Author

Adrian Baddeley , Rolf Turner and Ege Rubak .

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.

If the argument metric is given, it should be a distance metric (object of class "metric"). The disc with respect to this metric will be computed.

See Also

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

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(disc())/pi
 area(disc(mask=TRUE))/pi