grid.null                package:grid                R Documentation

Null Graphical Object

Description:

     These functions create a NULL graphical object, which has zero
     width, zero height, and draw nothing. It can be used as a
     place-holder or as an invisible reference point for other drawing.

Usage:

     nullGrob(x = unit(0.5, "npc"), y = unit(0.5, "npc"),
              default.units = "npc",
              name = NULL, vp = NULL)
     grid.null(...)

Arguments:

       x: A numeric vector or unit object specifying x-location.

       y: A numeric vector or unit object specifying y-location.

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. 

      vp: A Grid viewport object (or NULL).

     ...: Arguments passed to 'nullGrob()'.

Value:

     A null grob.

Author(s):

     Paul Murrell

See Also:

     Grid, 'viewport'

Examples:

     grid.newpage()
     grid.null(name="ref")
     grid.rect(height=grobHeight("ref"))
     grid.segments(0, 0, grobX("ref", 0), grobY("ref", 0))

