axis.POSIXct              package: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)

