\Header{grid.xaxis}{Draw an X-Axis}
\alias{xaxisGrob}{grid.xaxis}
\keyword{dplot}{grid.xaxis}
\begin{Description}\relax
These functions create and draw an x-axis.
\end{Description}
\begin{Usage}
\begin{verbatim}
grid.xaxis(at = NULL, label = TRUE, main = TRUE, name = NULL, gp = gpar(),
           draw = TRUE, vp = NULL)
xaxisGrob(at = NULL, label = TRUE, main = TRUE, name = NULL, gp = gpar(),
         vp = NULL)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{at}] A numeric vector of x-value locations for the tick marks.
\item[\code{label}] A logical value indicating whether to draw the labels
on the tick marks.
\item[\code{main}] A logical value indicating whether to draw the axis
at the bottom (\code{TRUE}) or at the top (\code{FALSE}) of the
viewport.
\item[\code{name}] A character identifier. 
\item[\code{gp}] An object of class \code{gpar}, typically the output
from a call to the function \code{gpar}.  This is basically
a list of graphical parameter settings.
\item[\code{draw}] A logical value indicating whether graphics output
should be produced.
\item[\code{vp}] A Grid viewport obect (or \code{NULL}).
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
Both functions create an xaxis grob (a graphical object describing an
xaxis), but only \code{grid.xaxis}
draws the xaxis (and then only if \code{draw} is \code{TRUE}).
\end{Details}
\begin{Value}
An xaxis grob.  \code{grid.xaxis} returns the value invisibly.
\end{Value}
\begin{Section}{Children}
If the \code{at} slot of an xaxis grob is not \code{NULL} then
the xaxis will have the following children:
\describe{
\item[major] representing the line at the base of the
tick marks.
\item[ticks] representing the tick marks.
\item[labels] representing the tick labels.
}

If the \code{at} slot is \code{NULL} then there are no children
and ticks are drawn based on the current viewport scale.
\end{Section}
\begin{Author}\relax
Paul Murrell
\end{Author}
\begin{SeeAlso}\relax
\link{Grid},
\code{\Link{viewport}},
\code{\Link{grid.yaxis}}
\end{SeeAlso}

