\Header{symbols}{Draw symbols on a plot}
\keyword{aplot}{symbols}
\keyword{hplot}{symbols}
\keyword{multivariate}{symbols}
\begin{Description}\relax
This function draws symbols on a plot.  One of six symbols;
\emph{circles}, \emph{squares}, \emph{rectangles}, \emph{stars},
\emph{thermometers}, and \emph{boxplots}, can be plotted at a
specified set of x and y coordinates.  Specific aspects of the
symbols, such as relative size, can be customized by additional
parameters.
\end{Description}
\begin{Usage}
\begin{verbatim}
symbols(x, y = NULL, circles, squares, rectangles, stars,
        thermometers, boxplots, inches = TRUE, add = FALSE,
        fg = 1, bg = NA, xlab = NULL, ylab = NULL, main = NULL,
        xlim = NULL, ylim = NULL, ...)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{x, y}] the x and y co-ordinates for the symbols. They can be
specified in any way which is accepted by \code{\Link{xy.coords}}.
\item[\code{circles}] a vector giving the radii of the circles.
\item[\code{squares}] a vector giving the length of the sides of the squares.
\item[\code{rectangles}] a matrix with two columns.  The first column gives
widths and the second the heights of rectangle symbols.
\item[\code{stars}] a matrix with three or more columns giving the lengths
of the rays from the center of the stars.  \code{NA} values
are replaced by zeroes.
\item[\code{thermometers}] a matrix with three or four columns.  The first
two columns give the width and height of the thermometer symbols.
If there are three columns, the third is taken as a proportion.
The thermometers are filled from their base to this proportion
of their height.  If there are four columns, the third and fourth
columns are taken as proportions.  The thermometers are filled
between these two proportions of their heights.
\item[\code{boxplots}] a matrix with five columns.  The first two columns
give the width and height of the boxes, the next two columns
give the lengths of the lower and upper whiskers and the fifth
the proportion (with a warning if not in [0,1]) of the way up
the box that the median line is drawn.
\item[\code{inches}] If \code{inches} is \code{FALSE}, the units are taken
to be those of the x axis.  If \code{inches} is \code{TRUE},
the symbols are scaled so that the largest symbol is one
inch in height.  If a number is given the symbols are scaled to
make largest symbol this height in inches.
\item[\code{add}] if \code{add} is \code{TRUE}, the symbols are added to
an existing plot, otherwise a new plot is created.
\item[\code{fg}] colors the symbols are to be drawn in (the default is
the value of the \code{col} graphics parameter).
\item[\code{bg}] if specified, the symbols are filled with this color.
The default is to leave the symbols unfilled. 
\item[\code{xlab}] the x label of the plot if \code{add} is not true; this
applies to the following arguments as well.  Defaults to the
\code{\Link{deparse}}d expression used for \code{x}.
\item[\code{ylab}] the y label of the plot.
\item[\code{main}] a main title for the plot.
\item[\code{xlim}] numeric of length 2 giving the x limits for the plot.
\item[\code{ylim}] numeric of length 2 giving the y limits for the plot.
\item[\code{...}] graphics parameters can also be passed to this function,
as can the plot aspect ratio \code{asp} (see \code{\Link{plot.window}}).
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
Observations which have missing coordinates or missing size
parameters are not plotted.  The exception to this is \emph{stars}.
In that case, the length of any rays which are \code{NA} is reset
to zero.

Circles of radius zero are plotted at radius one pixel (which is
device-dependent).
\end{Details}
\begin{References}\relax
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
\emph{The New S Language}.
Wadsworth \& Brooks/Cole.

W. S. Cleveland (1985)
\emph{The Elements of Graphing Data.}
Monterey, California: Wadsworth.
\end{References}
\begin{SeeAlso}\relax
\code{\Link{stars}} for drawing \emph{stars} with a bit more
flexibility; \code{\Link{sunflowerplot}}.
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
x <- 1:10
y <- sort(10*runif(10))
z <- runif(10)
z3 <- cbind(z, 2*runif(10), runif(10))
symbols(x, y, thermometers=cbind(.5, 1, z), inches=.5, fg = 1:10)
symbols(x, y, thermometers = z3, inches=FALSE)
text(x,y, apply(format(round(z3, dig=2)), 1, paste, collapse = ","),
     adj = c(-.2,0), cex = .75, col = "purple", xpd=NA)

data(trees)
## Note that  example(trees)  shows more sensible plots!
N <- nrow(trees)
attach(trees)
## Girth is diameter in inches
symbols(Height, Volume, circles=Girth/24, inches=FALSE,
        main="Trees' Girth")# xlab and ylab automatically
## Colors too:
palette(rainbow(N, end = 0.9))
symbols(Height, Volume, circles=Girth/16, inches=FALSE, bg = 1:N,
        fg="gray30", main="symbols(*, circles=Girth/16, bg = 1:N)")
palette("default"); detach()
\end{ExampleCode}
\end{Examples}

