\HeaderA{grid.circle}{Draw a Circle}{grid.circle}
\aliasA{circleGrob}{grid.circle}{circleGrob}
\keyword{dplot}{grid.circle}
\begin{Description}\relax
Functions to create and draw a circle.
\end{Description}
\begin{Usage}
\begin{verbatim}
grid.circle(x=0.5, y=0.5, r=0.5, default.units="npc", name=NULL,
            gp=gpar(), draw=TRUE, vp=NULL)
circleGrob(x=0.5, y=0.5, r=0.5, default.units="npc", name=NULL,
            gp=gpar(), vp=NULL)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{x}] A numeric vector or unit object specifying x-locations.
\item[\code{y}] A numeric vector or unit object specifying y-locations.
\item[\code{r}] A numeric vector or unit object specifying radii.
\item[\code{default.units}] A string indicating the default units to use
if \code{x}, \code{y}, \code{width}, or \code{height}
are only given as numeric vectors.
\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 object (or NULL).
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
Both functions create a circle grob (a graphical object describing a
circle), but only \code{grid.circle()}
draws the circle (and then only if \code{draw} is \code{TRUE}).

The radius may be given in any
units;  if the units are \emph{relative} (e.g., \code{"npc"} or
\code{"native"}) then the radius will be different depending on
whether it is interpreted as a width or as a height.  In such cases,
the smaller of these two values will be the result.  To see the
effect, type \code{grid.circle()} and adjust the size of the window.
\end{Details}
\begin{Value}
A circle grob.  \code{grid.circle()} returns the value invisibly.
\end{Value}
\begin{Section}{Warning}
Negative values for the radius are silently converted to their
absolute value.
\end{Section}
\begin{Author}\relax
Paul Murrell
\end{Author}
\begin{SeeAlso}\relax
\LinkA{Grid}{Grid},
\code{\LinkA{viewport}{viewport}}
\end{SeeAlso}

