Extracting Plotting Structures
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, recyle (rep) the shorter
of x or y if their lengths differ.
|
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"
str(xy.coords(1:3, 1:2, recycle=TRUE))
str(xy.coords(-2:10,NULL, log="y"))
##> warning: 3 y values <=0 omitted ..