xy.coords
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 relevant R functions produces a measure of consistency.
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 |
xlab, ylab | names for the x and y variables to be extracted. |
log | character, |
recycle | logical; if |
setLab | logical indicating if the resulting |
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
.xvar
andyvar
are used as x and y variables. - list:
-
containing components
x
andy
, 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.frame
with 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
x
has 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
x | numeric (i.e., |
y | numeric vector of the same length as |
xlab |
|
ylab |
|
See Also
plot.default
, lines
, points
and lowess
are examples of functions which use this mechanism.
Examples
ff <- stats::fft(1:9) xy.coords(ff) xy.coords(ff, xlab = "fft") # labels "Re(fft)", "Im(fft)" 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 ..
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Licensed under the GNU General Public License.