surveillance (version 1.5-4)

discpoly: Generate a Polygon Representing a Disc/Circle (in Planar Coordinates)

Description

This functions generates a circle/disc represented as a polygon of one of three possible data classes: "gpc.poly", "owin", and "Polygon".

Usage

discpoly(center, r, npoly = 64, class = c("Polygon", "owin", "gpc.poly"),
         hole = FALSE)

Arguments

center

numeric vector of length two. Center coordinates of the circle.

r

numeric scalar. Radius of the circle.

npoly

integer. Number of edges of the polygonal approximation to the circle.

class

Which class of polygon should be generated? For spatstat's "owin" class, the disc function is used.

hole

logical. hole flag of the polygon.

Value

• Polygon of class class representing a circle/disc with npoly edges accuracy.

See Also

disc in package spatstat.

Examples

# Construct circle with increasing accuracy and of different spatial classes
disc1 <- discpoly(c(0,0), 5, npoly=4, class = "owin")
disc2 <- discpoly(c(0,0), 5, npoly=16, class = "Polygon")

library("spatstat")
print(disc1)
plot(disc1, axes=TRUE, main="", border=2)

print(disc2)
lines(disc2, col=3)

if (require("gpclib")) {
    oopt <- surveillance.options(gpclib=TRUE)
    disc3 <- discpoly(c(0,0), 5, npoly=64, class = "gpc.poly")
    print(disc3)
    plot(disc3, add=TRUE, poly.args=list(border=4))
    surveillance.options(oopt)
}

# if one only wants to draw a circle without an object behind
symbols(0, 0, circles=5, inches=FALSE, add=TRUE, fg=5)