R: Draw a Circle

grid.circle {grid}

R Documentation

Draw a Circle

Description

Functions to create and draw a circle.

Usage

grid.circle(x=0.5, y=0.5, r=0.5, default.units="npc", name=NULL,
            gp=gpar(), draw=TRUE, vp=NULL)
circleGrob(x=0.5, y=0.5, r=0.5, default.units="npc", name=NULL,
            gp=gpar(), vp=NULL)

Arguments

x

A numeric vector or unit object specifying x-locations.

y

A numeric vector or unit object specifying y-locations.

r

A numeric vector or unit object specifying radii.

default.units

A string indicating the default units to use if x, y, width, or height are only given as numeric vectors.

name

A character identifier.

gp

An object of class gpar, typically the output from a call to the function gpar. This is basically a list of graphical parameter settings.

draw

A logical value indicating whether graphics output should be produced.

vp

A Grid viewport object (or NULL).

Details

Both functions create a circle grob (a graphical object describing a circle), but only grid.circle() draws the circle (and then only if draw is TRUE).

The radius may be given in any units; if the units are relative (e.g., "npc" or "native") then the radius will be different depending on whether it is interpreted as a width or as a height. In such cases, the smaller of these two values will be the result. To see the effect, type grid.circle() and adjust the size of the window.

Value

A circle grob. grid.circle() returns the value invisibly.

Warning

Negative values for the radius are silently converted to their absolute value.

Author(s)

Paul Murrell