xy.coords
Extracting Plotting Structures
xy.coords is used by many functions to obtain
x and y coordinates for plotting. The use of this common mechanism
across all relevant R functions produces a measure of consistency.
- Keywords
- dplot
Usage
xy.coords(x, y = NULL, xlab = NULL, ylab = NULL, log = NULL,
recycle = FALSE, setLab = TRUE)Arguments
- x, y
the x and y coordinates of a set of points. Alternatively, a single argument
xcan be provided.- xlab, ylab
names for the x and y variables to be extracted.
- log
character,
"x","y"or both, as forplot. Sets negative values toNAand gives a warning.- recycle
logical; if
TRUE, recycle (rep) the shorter ofxoryif their lengths differ.- setLab
logical indicating if the resulting
xlabandylabshould be constructed from the “kind” of(x,y); otherwise, the argumentsxlabandylabare used.
Details
An attempt is made to interpret the arguments x and y in
a way suitable for bivariate plotting (or other bivariate procedures).
If y is NULL and x is a
- formula:
of the form
yvar ~ xvar.xvarandyvarare used as x and y variables.- list:
containing components
xandy, 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 or
data.framewith two or more columns: the first is assumed to contain the x values and the second the y values. Note that is also true if
xhas columns named"x"and"y"; these names will be irrelevant here.
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 setLab is true as by default).
If x (after transformation as above) inherits from class
"POSIXt" it is coerced to class "POSIXct".
Value
A list with the components
numeric (i.e., "double") vector of abscissa values.
numeric vector of the same length as x.
character(1) or NULL, the ‘label’ of
x.
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
library(grDevices)
# NOT RUN {
ff <- stats::fft(1:9)
xy.coords(ff)
xy.coords(ff, xlab = "fft") # labels "Re(fft)", "Im(fft)"
# }
# NOT RUN {
<!-- % dont -->
# }
# NOT RUN {
with(cars, xy.coords(dist ~ speed, NULL)$xlab ) # = "speed"
xy.coords(1:3, 1:2, recycle = TRUE) # otherwise error "lengths differ"
xy.coords(-2:10, log = "y")
##> xlab: "Index" \\ warning: 3 y values <= 0 omitted ..
# }