grid.circle               package: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

See Also:

     Grid, 'viewport'

