plot.window
Set up World Coordinates for Graphics Window
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).
- Keywords
- aplot
Usage
plot.window(xlim, ylim, log = "", asp = NA, …)Arguments
- xlim, ylim
numeric vectors 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, see ‘Details’.
- …
further graphical parameters as in
par. The relevant ones arexaxs,yaxsandlab.
Details
- asp:
If
aspis a finite positive value then the window is set up so that one data unit in the x direction is equal in length toasp\(\times\) one data unit in the y direction.Note that in this case,
par("usr")is no longer determined by, e.g.,par("xaxs"), but rather byaspand the device's aspect ratio. (See what happens if you interactively resize the plot device after running the example below!)The special case
asp == 1produces plots where distances between points are represented accurately on screen. Values withasp > 1can 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 graphical parameter xaxs or yaxs has value
"r" (which is the default).
To reverse an axis, use xlim or ylim of the form
c(hi, lo).
The function attempts to produce a plausible set of scales if one or
both of xlim and 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
plot, hist, image, …,
instead and refer to their help pages for explanation of the
arguments.
A side-effect of the call is to set up the usr, xaxp and
yaxp graphical parameters. (It is for the latter two that
lab is used.)
See Also
xy.coords,
plot.xy,
plot.default.
par for the graphical parameters mentioned.
Examples
library(graphics)
##--- 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)