trellis.par.get           package:lattice           R Documentation

Graphical Parameters for Trellis Displays

Description:

     Functions used to query, display and modify graphical parameters
     for fine control of Trellis displays.

Usage:

     trellis.par.get(name = NULL)
     trellis.par.set(name, value, warn)
     show.settings(x = NULL)
     lattice.theme

Arguments:

    name: character giving the name of a component. For a list of valid
          values type 'names(trellis.par.get())'. 

   value: a list giving the desired value of the component. 

    warn: logical, whether a warning should be issued when
          'trellis.par.get' is called when no graphics device is open 

       x: optional list of components that change the settings (any
          valid value of 'theme' in 'lset'). These are used to modify
          the current settings (obtained by 'trellis.par.get') before
          they are displayed 

Details:

     The various graphical parameters (color, line type, background
     etc) that control the look and feel of Trellis displays are highly
     customizable. Also, R can produce graphics on a number of devices,
     and it is expected that a different set of parameters would be
     more suited to different devices. These parameters are stored in a
     global variable named 'lattice.theme', which is a list whose
     components define settings for particular devices. The components
     are idenified by the name of the device they represent (as
     obtained by '.Device'), and are created as and when new devices
     are opened for the first time using 'trellis.device' (or Lattice
     plots are drawn on a device for the first time in that session).

     The initial settings for each device defaults to values
     appropriate for that device. In practice, this boils down to three
     distinct settings, one for screen devices like 'x11' and
     'windows', one for black and white plots (mostly useful for
     'postscript') and one for color printers (color 'postcript, pdf'). 

     Once a device is open, it's settings can be modified. When another
     instance of the same device is opened later using
     'trellis.device', the settings for that device are reset to its
     defaults, unless otherwise specified in the call to
     'trellis.device'. But settings for different devices are treated
     separately, i.e., opening a postscript device will not alter the
     x11 settings, which will remain in effect whenever an x11 device
     is active.

     The functions 'trellis.par.*' are meant to be interfaces to the
     global settings. They always apply on the settings for the
     currently ACTIVE device.

     'trellis.par.get', called without any arguments, returns the full
     list of settings for the active device. With the 'name' argument
     present, it returns that component only. 'trellis.par.get' sets
     the value of the 'name' component of the current active device
     settings to 'value'.

     'trellis.par.get' is usually used inside trellis functions to get
     graphical parameters before plotting. Modifications by users via
     'trellis.par.set' is typically done as follows:

     'add.line <- trellis.par.get("add.line")'

     'add.line$col <- "red"'

     'trellis.par.set("add.line", add.line)'

     The actual list of the components in 'trellis.settings' has not
     been finalized, so I'm not attempting to list them here. The
     current value can be obtained by 'print(trellis.par.get())'. Most
     names should be self-explanatory.

     'show.settings' provides a graphical display summarizing some of
     the values in the current setting.

     There are some simpler alternatives that can be used to manipulate
     the settings. Details can be found in the documentation for
     'lset'.

Value:

     'trellis.par.get' returns a list giving parameters for that
     component. If 'name' is missing, it returns the full list.

Author(s):

     Deepayan Sarkar deepayan@stat.wisc.edu

See Also:

     'trellis.device', 'lset', 'trellis.par.get','Lattice'

Examples:

     show.settings()

