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\name{C_06_update.trellis}
\alias{update.trellis}
\alias{[.trellis}
\alias{t.trellis}
\alias{trellis.last.object}
\title{Retrieve and Update Trellis Object}
\description{
Update method for objects of class \code{"trellis"}, and a way to retrieve
the last printed trellis object (that was saved).
}
\usage{
\method{update}{trellis}(object,
panel,
aspect,
as.table,
between,
key,
auto.key,
legend,
layout,
main,
page,
par.strip.text,
prepanel,
scales,
skip,
strip,
strip.left,
sub,
xlab,
ylab,
xlab.top,
ylab.right,
xlim,
ylim,
xscale.components,
yscale.components,
axis,
par.settings,
plot.args,
lattice.options,
index.cond,
perm.cond,
\dots)
\method{t}{trellis}(x)
\method{[}{trellis}(x, i, j, \dots, drop = FALSE)
trellis.last.object(\dots, prefix)
}
\arguments{
\item{object, x}{
The object to be updated, of class \code{"trellis"}.
}
\item{i, j}{ indices to be used. Names are not currently allowed. }
\item{drop}{
logical, whether dimensions with only one level are to be dropped.
Currently ignored, behaves as if it were \code{FALSE}.
}
% \item{warn}{
% logical, whether to warn when no plot is saved.
% }
\item{panel, aspect, as.table, between, key, auto.key, legend, layout,
main, page, par.strip.text, prepanel, scales, skip, strip,
strip.left, sub, xlab, ylab, xlab.top, ylab.right, xlim, ylim,
xscale.components, yscale.components, axis, par.settings, plot.args,
lattice.options, index.cond, perm.cond, \dots}{
arguments that will be used to update \code{object}. See details
below.
}
\item{prefix}{
A character string acting as a prefix identifying the plot of a
\code{"trellis"} object. Only relevant when a particular page is
occupied by more than one plot. Defaults to the value appropriate
for the last \code{"trellis"} object printed. See
\code{\link{trellis.focus}}.
}
}
\details{
All high level lattice functions such as \code{xyplot} produce an
object of (S3) class \code{"trellis"}, which is usually displayed by its
\code{print} method. However, the object itself can be manipulated and
modified to a large extent using the \code{update} method, and then
re-displayed as needed.
Most arguments to high level functions can also be supplied to the
\code{update} method as well, with some exceptions. Generally
speaking, anything that would needs to change the data within each
panel is a no-no (this includes the \code{formula, data, groups,
subscripts} and \code{subset}). Everything else is technically game,
though might not be implemented yet. If you find something missing
that you wish to have, feel free to make a request.
Not all arguments accepted by a Lattice function are processed by
\code{update}, but the ones listed above should work. The purpose of
these arguments are described in the help page for
\code{\link{xyplot}}. Any other argument is added to the list of
arguments to be passed to the \code{panel} function. Because of their
somewhat special nature, updates to objects produced by \code{cloud}
and \code{wireframe} do not work very well yet.
The \code{"["} method is a convenient shortcut for updating
\code{index.cond}. The \code{t} method is a convenient shortcut for
updating \code{perm.cond} in the special (but frequent) case where
there are exactly two conditioning variables, when it has the effect
of switching (\sQuote{transposing}) their order.
The print method for \code{"trellis"} objects optionally saves the
object after printing it. If this feature is enabled,
\code{trellis.last.object} can retrieve it. By default, the last
object plotted is retrieved, but if multiple objects are plotted on
the current page, then others can be retrieved using the appropriate
\code{prefix} argument. If \code{\link{trellis.last.object}} is
called with arguments, these are used to update the retrieved object
before returning it.
}
% WAS: \dontrun{
% trellis.last.object(xlab = "Year")
% }
\examples{
spots <- by(sunspots, gl(235, 12, labels = 1749:1983), mean)
old.options <- lattice.options(save.object = TRUE)
xyplot(spots ~ 1749:1983, xlab = "", type = "l",
scales = list(x = list(alternating = 2)),
main = "Average Yearly Sunspots")
update(trellis.last.object(), aspect = "xy")
trellis.last.object(xlab = "Year")
lattice.options(old.options)
}
\value{
An object of class \code{trellis}, by default plotted by
\code{print.trellis}. \code{trellis.last.object} returns
\code{NULL} is no saved object is available.
}
\author{ Deepayan Sarkar \email{Deepayan.Sarkar@R-project.org}}
\seealso{
\code{\link{trellis.object}}, \code{\link{Lattice}},
\code{\link{xyplot}}
}
\keyword{dplot}
|
