R: Initializing Trellis Displays

trellis.device {lattice}

R Documentation

Initializing Trellis Displays

Description

Initialization of a display device with appropriate graphical parameters.

Usage

trellis.device(device = getOption("device"),
               color = !(dev.name == "postscript"),
               theme = lattice.getOption("default.theme"),
               new = TRUE,
               retain = FALSE,
               ...)
canonical.theme(name, color)
col.whitebg()

Arguments

`device`	function (or the name of one as a character string) that starts a device. Admissible values depend on the platform and how R was compiled (see `Devices`), but usually `"pdf"`, `"postscript"`, `"png"`, `"jpeg"` and at least one of `"X11"`, `"windows"` and `"quartz"` will be available.
`color`	logical, whether the display should be color or black and white. Defaults to `FALSE` for postscript devices, `TRUE` otherwise.
`theme`	list of components that changes the settings of the device opened, or, a function that when called produces such a list. The function name can be supplied as a quoted string. These settings are only used to modify the default settings (determined by other arguments), and need not contain all possible parameters. A possible use of this argument is to change the default settings by specifying `lattice.options(default.theme = "col.whitebg")`. For back-compatibility, this is initially (when lattice is loaded) set to `options(lattice.theme)`. If `theme` is a function, it will not be supplied any arguments, however, it is guaranteed that a device will already be open when it is called, so one may use `.Device` inside the function to ascertain what device has been opened.
`new`	logical flag indicating whether a new device should be started. If `FALSE`, the options for the current device are changed to the defaults determined by the other arguments.
`retain`	logical. If `TRUE` and a setting for this device already exists, then that is used instead of the defaults for this device. By default, pre-existing settings are overwritten (and lost).
`name`	name of the device for which the setting is required, as returned by `.Device`
`...`	additional parameters to be passed to the `device` function, most commonly `file` for non-screen devices, as well as `height`, `width`, etc. See the help file for individual devices for admissible arguments.

Details

Trellis Graphics functions obtain the default values of various graphical parameters (colors, line types, fonts, etc.) from a customizable “settings” list. This functionality is analogous to par for standard R graphics and, together with lattice.options, mostly supplants it (par settings are mostly ignored by Lattice). Unlike par, Trellis settings can be controlled separately for each different device. canonical.theme and col.whitebg produce predefined settings (a.k.a. themes), while trellis.device provides a high level interface to control which “theme” will be in effect when a new device is opened. trellis.device is called automatically when a "trellis" object is plotted, and the defaults can be used to provide sufficient control, so in a properly configured system it is rarely necessary for the user to call trellis.device explicitly.

The canonical.theme function is intended to provide device specific settings (e.g. light colors on a grey background for screen devices, dark colors or black and white for print devices) which were used as defaults prior to R 2.3.0. However, these defaults are not always appropriate, due to the variety of platforms and hardware settings on which R is used, as well as the fact that a plot created on a particular device may be subsequently used in many different ways. For this reason, a “safe” default is used for all devices from R 2.3.0 onwards. The old behaviour can be reinstated by setting canonical.theme as the default theme argument, e.g. by putting options(lattice.theme = "canonical.theme") in a startup script (see the entry for theme above for details).

Value

canonical.theme returns a list of components defining graphical parameter settings for Lattice displays. It is used internally in trellis.device, and can also be used as the theme argument to trellis.par.set, or even as theme in trellis.device to use the defaults for another device.
col.whitebg returns a similar (but smaller) list that is suitable as the theme argument to trellis.device and trellis.par.set. It contains settings values which provide colors suitable for plotting on a white background. Note that the name col.whitebg is somewhat a misnomer, since it actually sets the background to transparent rather than white.

Note

Earlier versions of trellis.device had a bg argument to set the background color, but this is no longer supported. If supplied, the bg argument will be passed on to the device function; however, this will have no effect on the Trellis settings. It is rarely meaningful to change the background alone; if you feel the need to change the background, consider using the theme argument instead.

Author(s)

Deepayan Sarkar Deepayan.Sarkar@R-project.org