R: Extracting Plotting Structures

xy.coords {base}

R Documentation

Extracting Plotting Structures

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.

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 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.

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.

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"

str(xy.coords(1:3, 1:2, recycle=TRUE))
str(xy.coords(-2:10,NULL, log="y")) 
##> warning: 3 y values <=0 omitted ..

[Package base version 1.1 ]