axis.POSIXct
Date and Date-time Plotting Functions
Functions to plot objects of classes "POSIXlt",
"POSIXct" and "Date" representing calendar dates and times.
Usage
axis.POSIXct(side, x, at, format, labels = TRUE, ...)
axis.Date(side, x, at, format, labels = TRUE, ...)Arguments
- x, at
- A date-time or date object.
- side
- See
axis. - format
- See
strptime. - labels
- Either a logical value specifying whether annotations are to be made at the tickmarks, or a vector of character strings to be placed at the tickpoints.
- ...
- Further arguments to be passed from or to other methods, typically graphical parameters.
Details
axis.POSIXct and axis.Date work quite hard to choose
suitable time units (years, months, days, hours, minutes or seconds)
and a sensible output format, but this can be overridden by supplying
a format specification.
If at is supplied it specifies the locations of the ticks
and labels whereas if x is specified a suitable grid of labels
is chosen. Printing of tick labels can be suppressed by using
labels = FALSE.
The date-times for a "POSIXct" input are interpreted in the
time zone give by the "tzone" attribute if there is one,
otherwise the current time zone.
The way the date-times are rendered (especially month names) is
controlled by the locale setting of category "LC_TIME" (see
Sys.setlocale.
Value
-
The locations on the axis scale at which tick marks were drawn.
Note
These functions are the workhorse for methods for Axis.
Prior to R 2.12.0 there were also plot methods for the
date-time classes, but the default method has also handled those for a
long time.
See Also
DateTimeClasses, Dates for details of the classes.
Axis.
Examples
library(graphics)
with(beaver1, {
time <- strptime(paste(1990, day, time %/% 100, time %% 100),
"%Y %j %H %M")
plot(time, temp, type = "l") # axis at 4-hour intervals.
# now label every hour on the time axis
plot(time, temp, type = "l", xaxt = "n")
r <- as.POSIXct(round(range(time), "hours"))
axis.POSIXct(1, at = seq(r[1], r[2], by = "hour"), format = "%H")
})
plot(.leap.seconds, seq_along(.leap.seconds), type = "n", yaxt = "n",
xlab = "leap seconds", ylab = "", bty = "n")
rug(.leap.seconds)
## or as dates
lps <- as.Date(.leap.seconds)
plot(lps, seq_along(.leap.seconds),
type = "n", yaxt = "n", xlab = "leap seconds",
ylab = "", bty = "n")
rug(lps)
## 100 random dates in a 10-week period
random.dates <- as.Date("2001/1/1") + 70*sort(stats::runif(100))
plot(random.dates, 1:100)
# or for a better axis labelling
plot(random.dates, 1:100, xaxt = "n")
axis.Date(1, at = seq(as.Date("2001/1/1"), max(random.dates)+6, "weeks"))
axis.Date(1, at = seq(as.Date("2001/1/1"), max(random.dates)+6, "days"),
labels = FALSE, tcl = -0.2)