oce.axis.POSIXct {oce} | R Documentation

## Oce Version of axis.POSIXct

### Description

A specialized variant of `axis.POSIXct` that produces results with less ambiguity in axis labels.

### Usage

    oce.axis.POSIXct(side, x, at, tformat, labels = TRUE,
      drawTimeRange = getOption("oceDrawTimeRange"),
      abbreviateTimeRange = FALSE, drawFrequency = FALSE, cex = par("cex"),
      cex.axis = par("cex.axis"), cex.main = par("cex.main"),
      mar = par("mar"), mgp = par("mgp"), main = "",
      debug = getOption("oceDebug"), ...)

### Arguments

`side` | as for `axis.POSIXct`.
`x` | as for `axis.POSIXct`.
`at` | as for `axis.POSIXct`.
`tformat` | as `format` for `axis.POSIXct` for now, but may eventually have new features for multiline labels, e.g. day on one line and month on another.
`labels` | as for `axis.POSIXct`.
`drawTimeRange` | boolean, `TRUE` to draw a time range on the opposite side of the plot.
`abbreviateTimeRange` | boolean, `TRUE` to abbreviate the second number in the time range, e.g. dropping the year if it is the same in the first number.
`drawFrequency` | boolean, `TRUE` to show the frequency of sampling in the data
`cex` | size of labels on axes; see `par`("cex").
`cex.axis` | see `par`("cex.axis").
`cex.main` | see `par`("cex.main").
`mar` | value for `par(mar)` for axis
`mgp` | value for `par(mgp)` for axis
`main` | title of plot
`debug` | a flag that turns on debugging. Set to 1 to get a moderate amount of debugging information, or to 2 to get more.
`...` | as for `axis.POSIXct`.

### Details

The tick marks are set automatically based on examination of the time range on the axis. The scheme was devised by constructing test cases with a typical plot size and font size, and over a wide range of time scales. In some categories, both small tick marks are interspersed between large ones.

The user may set the format of axis numbers with the `tformat` argument. If this is not supplied, the format is set based on the time span of the axis:

- If this time span is less than a minute, the time axis labels are in seconds (fractional seconds, if the interval is less than 2 seconds), with leading zeros on small integers. (Fractional seconds are enabled with a trick: the usual R format `"%S"` is supplemented with a new format e.g. `"%.2S"`, meaning to use two digits after the decimal.)

- If the time span exceeds a minute but is less than 1.5 days, the label format is `"%H:%M:%S"`.

- If the time span exceeds 1.5 days but is less than 1 year, the format is `"%b %d"` (e.g. Jul 15) and, again, the tick marks are set up for several subcategories.

- If the time span exceeds a year, the format is `"%Y"`, i.e. the year is displayed with 4 digits.

It should be noted that this scheme differs from the R approach in several ways. First, R writes day names for some time ranges, in a convention that is seldom seen in the literature. Second, R will write nn:mm for both HH:MM and MM:SS, an ambiguity that might confuse readers. Third, the use of both large and small tick marks is not something that R does.

Bear in mind that `tformat` may be set to alter the number format, but that the tick mark scheme cannot (presently) be controlled.

### Value

A vector of times corresponding to axis ticks is returned silently.

### Author(s)

Dan Kelley

### See Also

This is used mainly by `oce.plot.ts`.

[Package oce version 0.9-20 Index]