R: Set up World Coordinates for Graphics Window

Set up World Coordinates for Graphics Window

Usage

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

Arguments

`xlim, ylim`	numeric of length 2, giving the x and y coordinates ranges.
`log`	character; indicating which axes should be in log scale.
`asp`	numeric, giving the aspect ratio y/x.
`...`	further graphical parameters as in `par(..)`.

Description

This function sets up the world coordinate system for a graphics window. It is called by higher level functions such as plot.default (after plot.new).

Details

Note that if 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 asp * one data unit in the y direction.

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

Usually, one should rather use the higher level functions such as plot, hist, image, ..., instead and refer to their help pages for explanation of the arguments.

Examples

##--- An example for the use of  `asp' :
library(mva)
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=0.5)