R: Set up World Coordinates for Graphics Window

plot.window {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 aspect ratio y/x, see ‘Details’.
`...` | 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 y direction is equal in length to `asp` * one data unit in the x 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.

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

    ##--- 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)

[Package graphics version 4.0.5 Index]