\Header{plot.window}{Set up World Coordinates for Graphics Window}
\keyword{aplot}{plot.window}
\begin{Description}\relax
This function sets up the world coordinate system for a graphics
window.  It is called by higher level functions such as
\code{\Link{plot.default}} (\emph{after} \code{\Link{plot.new}}).
\end{Description}
\begin{Usage}
\begin{verbatim}
plot.window(xlim, ylim, log = "", asp = NA, ...)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{xlim, ylim}] numeric of length 2, giving the x and y coordinates
ranges.
\item[\code{log}] character; indicating which axes should be in log scale.
\item[\code{asp}] numeric, giving the \bold{asp}ect ratio y/x.
\item[\code{...}] further graphical parameters as in \code{\Link{par}}.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
Note that if \code{asp} is a finite positive value then the window is
set up so that one data unit in the x direction is equal in length to
\code{asp} \eqn{\times}{*} one data unit in the y direction.

The special case \code{asp == 1} produces plots where distances
between points are represented accurately on screen.  Values with
\code{asp > 1} can be used to produce more accurate maps when using
latitude and longitude.

The function attempts to produce a plausible set of scales if one or
both of \code{xlim} and \code{ylim} is of length one or the two values
given are identical, but it is better to avoid that case.

Usually, one should rather use the higher level functions such as
\code{\Link{plot}}, \code{\Link{hist}}, \code{\Link{image}}, \dots,
instead and refer to their help pages for explanation of the
arguments.
\end{Details}
\begin{SeeAlso}\relax
\code{\Link{xy.coords}},
\code{\Link{plot.xy}},
\code{\Link{plot.default}}.
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
##--- An example for the use of 'asp' :
library(stats)  # normally loaded
data(eurodist)
loc <- cmdscale(eurodist)
rx <- range(x <- loc[,1])
ry <- range(y <- -loc[,2])
plot(x, y, type="n", asp=1, xlab="", ylab="")
abline(h = pretty(rx, 10), v = pretty(ry, 10), col = "lightgray")
text(x, y, names(eurodist), cex=0.8)
\end{ExampleCode}
\end{Examples}

