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\name{G_panel.number}
\alias{current.row}
\alias{current.column}
\alias{packet.number}
\alias{panel.number}
\alias{which.packet}
\alias{trellis.currentLayout}
\title{Accessing Auxiliary Information During Plotting}
\description{
Control over lattice plots are provided through a collection of user
specifiable functions that perform various tasks during the plotting.
Not all information is available to all functions. The functions
documented here attempt to provide a consistent interface to access
relevant information from within these user specified functions,
namely those specified as the \code{panel}, \code{strip} and
\code{axis} functions. Note that this information is not available to
the \code{prepanel} function, which is executed prior to the actual
plotting.
}
\usage{
current.row(prefix)
current.column(prefix)
panel.number(prefix)
packet.number(prefix)
which.packet(prefix)
trellis.currentLayout(which = c("packet", "panel"), prefix)
}
\arguments{
\item{which}{
whether return value (a matrix) should contain panel numbers or
packet numbers, which are usually, but not necessarily, the same
(see below for details).
}
\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}}.
}
}
\value{
\code{trellis.currentLayout} returns a matrix with as many rows and
columns as in the layout of panels in the current plot. Entries in
the matrix are integer indices indicating which packet (or panel; see
below) occupies that position, with 0 indicating the absence of a
panel. \code{current.row} and \code{current.column} return integer
indices specifying which row and column in the layout are currently
active. \code{panel.number} returns an integer counting which panel
is being drawn (starting from 1 for the first panel, a.k.a. the panel
order). \code{packet.number} gives the packet number according to the
packet order, which is determined by varying the first conditioning
variable the fastest, then the second, and so on. \code{which.packet}
returns the combination of levels of the conditioning variables in the
form of a numeric vector as long as the number of conditioning
variables, with each element an integer indexing the levels of the
corresponding variable.
}
\note{
The availability of these functions make redundant some features
available in earlier versions of lattice, namely optional arguments
called \code{panel.number} and \code{packet.number} that were made
available to \code{panel} and \code{strip}. If you have written such
functions, it should be enough to replace instances of
\code{panel.number} and \code{packet.number} by the corresponding
function calls. You should also remove \code{panel.number} and
\code{packet.number} from the argument list of your function to avoid
a warning.
If these accessor functions are not enough for your needs, feel free
to contact the maintainer and ask for more.
}
\seealso{
\code{\link{Lattice}}, \code{\link{xyplot}}
}
\author{ Deepayan Sarkar \email{Deepayan.Sarkar@R-project.org}}
\keyword{dplot}
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