| trellis.par.get {lattice} | R Documentation |
Functions used to query, display and modify graphical parameters for fine control of Trellis displays. Modifications are made to the settings for the currently active device only.
trellis.par.set(name, value, ..., theme, warn = TRUE) trellis.par.get(name = NULL) show.settings(x = NULL)
name |
character giving the name of a component. If unspecified,
names(trellis.par.get()) returns a list containing all the
current settings (this can be used to get the valid values for
name)
|
value |
a list giving the desired value of the component. Components that
are already defined as part of the current settings but are not
mentioned in value will remain unchanged.
|
theme |
a list decribing how to change the settings, similar to what is
returned by trellis.par.get(). This is purely for
convenience, allowing multiple calls to trellis.par.set to be
condensed into one. The name of each component must be a valid
name as described above, with the corresponding value a valid
value as described above.
As in trellis.device, theme can also be a
function that produces such a list when called. The function name
can be supplied as a quoted string.
|
... |
Multiple settings can be specified in name = value form.
Equivalent to calling with theme = list(...)
|
warn |
logical, indicating 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). These are used to modify the current
settings (obtained by trellis.par.get) before they are
displayed.
|
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 internally in a
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, its 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 traditionally done as follows:
add.line <- trellis.par.get("add.line")
add.line$col <- "red"
trellis.par.set("add.line", add.line)
More convenient (but not S compatible) ways to do this are
trellis.par.set(list(add.line = list(col = "red")))
and
trellis.par.set(add.line = list(col = "red"))
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 settings.
trellis.par.get returns a list giving parameters for that
component. If name is missing, it returns the full list.
In some ways, trellis.par.get and trellis.par.set
together are a replacement for the par function used in
traditional R graphics. In particular, changing par settings
has little (if any) effect on lattice output. Since lattice plots are
implemented using Grid graphics, its parameter system does have
an effect unless overridden by a suitable lattice parameter setting.
Such parameters can be specified as part of a lattice theme by
including them in the grid.pars component (see
gpar for a list of valid parameter names).
One of the uses of par is to set par(ask = TRUE) making
R wait for user input before starting a new graphics page. For Grid
graphics, this is done using
grid.prompt. Lattice has no separate
interface for this, and the user must call grid.prompt
directly. If the grid package is not attached (lattice itself
only loads the grid namespace), this may be done using
grid::grid.prompt(TRUE).
Deepayan Sarkar Deepayan.Sarkar@R-project.org
trellis.device, Lattice,
grid.prompt,
gpar
show.settings()