plot.window             package:graphics             R Documentation

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
     'plot.default' (_after_ 'plot.new').

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 *asp*ect ratio y/x, see below.

     ...: further graphical parameters as in 'par'. The relevant ones
          are 'xaxs', 'yaxs' and 'lab'. 

Details:

     asp: 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.

          Note that in this case, 'par("usr")' is no longer determined
          by, e.g., 'par("xaxs")', but rather by '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 '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.

     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'.

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)

