axis.POSIXct {base}

R Documentation

Date-time Plotting Functions

Description

Functions to manipulate objects of classes "POSIXlt" and "POSIXct" representing calendar dates and times (to the nearest second).

Usage

plot.POSIXct(x, y, xlab = "", ...)
plot.POSIXlt(x, y, xlab = "", ...)
axis.POSIXct(side, x, at, format, ...)

Arguments

x, at	A date-time object.
y	numeric values to be plotted against x.
xlab	a character string giving the label for the x axis.
side	See axis.
format	See strptime.
...	Further arguments to be passed from or to other methods, typically graphical parameters.

Details

The functions plot against an x-axis of date-times. axis.POSIXct works 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 for axis.POSIXct it specifies the locations of the ticks and labels: if x is specified a suitable grid of labels is chosen.

See Also

DateTimeClasses for details of the classes.

Examples

if(require(MASS, quietly = TRUE)) {
data(beav1)
attach(beav1)
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")
rm(time)
detach(beav1)
detach(package:MASS)
}

plot(.leap.seconds, 1:22, type="n", yaxt="n",
     xlab="leap seconds", ylab="", bty="n")
rug(.leap.seconds)

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