Compute Axis Tickmark Locations (For POSIXct Axis)

Compute pretty tickmark locations, the same way as R does internally. By default, gives the at values which axis.POSIXct(side, x) would use.

axTicks.POSIXct(side, x, at, format, labels = TRUE, ...)

axTicks.Date(side = 1, x, ...)

Arguments

side: See axis.
x, at: A date-time or date object.
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.

Details

axTicks has no implementation for POSIXct axis. This function fills the gap.

Value

numeric vector of coordinate values at which axis tickmarks can be drawn.

Author

Andri Signorell <andri@signorell.net> simply copying R-Core code

Examples

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")
  # place the grid
  abline(v=axTicks.POSIXct(1, at = seq(r[1], r[2], by = "hour"), format = "%H"),
         col="grey", lty="dotted")
})