\Header{panel.barchart}{Default Panel Function for barchart}
\keyword{dplot}{panel.barchart}
\begin{Description}\relax
Default panel function for \code{barchart}.
\end{Description}
\begin{Usage}
\begin{verbatim}
panel.barchart(x, y, box.ratio = 1,
               horizontal = TRUE,
               origin = NULL, reference = TRUE,
               stack = FALSE,
               groups = NULL, 
               col = if (is.null(groups)) bar.fill$col else
               regions$col,
               ...)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{x}] Extent of Bars. By default, bars start at left of panel,
unless \code{origin} is specified, in which case they start there

\item[\code{y}] Horizontal location of bars, possibly factor
\item[\code{box.ratio}] ratio of bar width to inter-bar space
\item[\code{horizontal}] logical. If FALSE, the plot is `transposed' in the
sense that the behaviours of x and y are switched. x is now
the `factor'.  Interpretation of other arguments change
accordingly. See documentation of \code{bwplot} for a fuller
explanation.

\item[\code{origin}] origin of the bars. For grouped displays with
\code{stack = TRUE}, this argument is ignored and the origin set to
0. Otherwise, defaults to \code{NULL}, in which case bars start at
leftmost end of panel.

\item[\code{reference}] logical, whether a reference line is to be drawn at
the origin

\item[\code{stack}] logical, relevant when groups is non-null. If
\code{FALSE} (the default), bars for different values of the
grouping variable are drawn side by side, otherwise they are
stacked.

\item[\code{groups}] optional grouping variable
\item[\code{col}] Color of the bars. By default, the trellis parameter
\code{bar.fill} is used if there is no grouping variable, otherwise
\code{regions} is used. 

\item[\code{...}] extra arguments will be accepted but ignored 
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
A barchart is drawn in the panel. Note that most arguments controlling
the display can be supplied to the high-level \code{barchart} call
directly.
\end{Details}
\begin{Author}\relax
Deepayan Sarkar \email{deepayan@stat.wisc.edu}
\end{Author}
\begin{SeeAlso}\relax
\code{\Link{barchart}}
\end{SeeAlso}

