\HeaderA{panel.barchart}{Default Panel Function for barchart}{panel.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, box.width,
               horizontal = TRUE,
               origin = NULL, reference = TRUE,
               stack = FALSE,
               groups = NULL, 
               col = if (is.null(groups)) plot.polygon$col
                     else superpose.polygon$col,
               border = if (is.null(groups)) plot.polygon$border
                        else superpose.polygon$border,
               lty = if (is.null(groups)) plot.polygon$lty
                     else superpose.polygon$lty, 
               lwd = if (is.null(groups)) plot.polygon$lwd
                     else superpose.polygon$lwd,
               ...)
\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{box.width}] thickness of bars in absolute units; overrides
\code{box.ratio}.  Useful for specifying thickness when the
categorical variable is not a factor, as use of \code{box.ratio}
alone cannot achieve a thickness greater than 1. 
\item[\code{horizontal}] logical. If FALSE, the plot is \sQuote{transposed} in the sense that
the behaviours of x and y are switched. x is now the
\sQuote{factor}.  Interpretation of other arguments change
accordingly. See documentation of \code{\LinkA{bwplot}{bwplot}} for a fuller
explanation.

\item[\code{origin}] the origin for 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
the left (or bottom) end of a panel.  This choice is somewhat
unfortuntate, as it can be misleading, but is the default for
historical reasons.  For tabular (or similar) data, \code{origin =
      0} is usually more appropriate; if not, one should reconsider the
use of a bar chart in the first place (dot plots are often a good
alternative).

\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, border, lty, lwd}] Graphical parameters for the bars. By default, the trellis parameter
\code{plot.polygon} is used if there is no grouping variable, otherwise
\code{superpose.polygon} is used.  \code{col} gives the fill color,
\code{border} the border color, and \code{lty} and \code{lwd} the
line type and width of the borders.

\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.Sarkar@R-project.org}
\end{Author}
\begin{SeeAlso}\relax
\code{\LinkA{barchart}{barchart}}
\end{SeeAlso}

