The R Project SVN R

% File src/library/graphics/man/plot.window.Rd

% Part of the R package, https://www.R-project.org

% Copyright 1995-2014 R Core Team

% Distributed under GPL 2 or later

\name{plot.window}

\alias{plot.window}

\alias{xlim}

\alias{ylim}

\alias{asp}

\concept{aspect ratio}

\concept{log scale}

\concept{axis range}

\title{Set up World Coordinates for Graphics Window}

\description{

  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}}).

}

\usage{

plot.window(xlim, ylim, log = "", asp = NA, \dots)

}

\arguments{

  \item{xlim, ylim}{numeric vectors of length 2, giving the x and y

    coordinates ranges.}

  \item{log}{character; indicating which axes should be in log scale.}

  \item{asp}{numeric, giving the \bold{asp}ect ratio y/x,

    see \sQuote{Details}.}

  \item{\dots}{further \link{graphical parameters} as in \code{\link{par}}.

    The relevant ones are \code{xaxs}, \code{yaxs} and \code{lab}.

  }

}

\details{

  \describe{

    \item{asp:}{

      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.

      Note that in this case, \code{\link{par}("usr")} is no longer

      determined by, e.g., \code{par("xaxs")}, but rather by \code{asp} and

      the device's aspect ratio.  (See what happens if you interactively

      resize the plot device after running the example below!)

      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.

  }}

  Note that the coordinate ranges will be extended by 4\% if the

  appropriate \link{graphical parameter} \code{xaxs} or \code{yaxs} has value

  \code{"r"} (which is the default).

  To reverse an axis, use \code{xlim} or \code{ylim} of the form

  \code{c(hi, lo)}.

  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.

  A side-effect of the call is to set up the \code{usr}, \code{xaxp} and

  \code{yaxp} \link{graphical parameters}.  (It is for the latter two that

  \code{lab} is used.)

}

\seealso{

  \code{\link{xy.coords}},

  \code{\link{plot.xy}},

  \code{\link{plot.default}}.

  \code{\link{par}} for the graphical parameters mentioned.

}

\examples{

##--- An example for the use of 'asp' :

require(stats)  # normally loaded

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, labels(eurodist), cex = 0.8)

}

\keyword{aplot}