xy.coords {grDevices}R Documentation

Extracting Plotting Structures

Description

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

Usage

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

Arguments

x, y the x and y coordinates of a set of points. Alternatively, a single argument x can be provided.
xlab,ylab names for the x and y variables to be extracted.
log character, "x", "y" or both, as for plot. Sets negative values to NA and gives a warning.
recycle logical; if TRUE, recycle (rep) the shorter of x or y if their lengths differ.

Details

An attempt is made to interpret the arguments x and y in a way suitable for plotting.

If y is missing and x is a

formula:
of the form yvar ~ xvar. xvar and yvar are used as x and y variables.
list:
containing components x and y, these are used to define plotting coordinates.
time series:
the x values are taken to be time(x) and the y values to be the time series.
matrix with two columns:
the first is assumed to contain the x values and the second the y values.

In any other case, the x argument is coerced to a vector and returned as y component where the resulting x is just the index vector 1:n. In this case, the resulting xlab component is set to "Index".

If x (after transformation as above) inherits from class "POSIXt" it is coerced to class "POSIXct".

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.

See Also

plot.default, lines, points and lowess are examples of functions which use this mechanism.

Examples

xy.coords(stats::fft(c(1:10)), NULL)

with(cars, xy.coords(dist ~ speed, NULL)$xlab ) # = "speed"

xy.coords(1:3, 1:2, recycle=TRUE)
xy.coords(-2:10,NULL, log="y")
##> warning: 3 y values <=0 omitted ..
[Package grDevices version 2.2.1 Index]