## Extracting Plotting Structures

## Usage

    xy.coords(x, y, xlab=NULL, ylab=NULL)

## Arguments

`x,y` | the x and y coordinates of a set of points. Alternatively, a single argument `x` can be be provided. In this case, an attempt is made to interpret the argument in a way suitable for plotting. If the argument is a formula `yvar ~ xvar`, `xvar` and `yvar` are used as x and y variables; if the argument is a list containing components `x` and `y`, these are used are assumed to define plotting coordinates; if the argument contains a time series, the x values are taken to be time and the y values to be the time series; if the argument is a matrix with two columns, the first is assumed to contain the x values and the second the y values; in any other case, the argument is coerced to a vector and the values plotted against their indices.
`xlab,ylab` | names for the x and y variables to be extracted.

## Description

`xy.coords` is used by many function to obtain x and y coordinates for plotting. The use of this common mechanism across all R functions produces a measure of consistency.

`plot.default` and `lowess` are examples of functions which use this mechanism.

## Value

A list with the components

`x` | numeric (i.e. `"double"`) vector of abscissa values.
`y` | numeric vector of the same length as `x`.
`xlab` | `character(1)` or `NULL`, the `label' of `x`.
`ylab` | `character(1)` or `NULL`, the `label' of `y`.

## Examples

    xy.coords(fft(c(1:10)), NULL)
    data(cars) ; attach(cars)
    xy.coords(dist ~ speed, NULL)$xlab # = "speed"

[Package Contents]