dive {scuba}

Define a Dive Profile

Description

Define a dive profile.

Usage

  dive(..., begin=0, end=0, tanklist=NULL)

Arguments

...

Any number of arguments, specifying a sequence of events that make up the dive. The arguments may specify depths, time spent at each depth, ascent or descent rates, and gas switches. See Details.

begin, end

The depths at the start and finish of the dive (normally zero indicating that the dive starts and finishes at the surface) or NA.

tanklist

Optional list of the gases contained in each tank, for a dive with multiple tanks.

Details

This function creates an object of class "dive" which represents a scuba dive. The dive profile is assumed to be piecewise linear, that is, the graph of depth against time is a broken straight line. Dives are assumed to start and finish at the surface.

The arguments ... specify a succession of events that make up the dive. Each argument can be

a vector of length 2

interpreted as c(depth, duration) where depth gives the depth in metres and duration the length of stay at this depth, in minutes.

a single number

interpreted as a waypoint depth in metres. The diver will ascend or descend to this depth, at the current default rate of ascent or descent.

an object of class "gas"

specifying a breathing gas. Such objects are created by the functions nitrox and trimix. The diver switches to this gas.

an argument of the form tank=n

specifying a switch to another tank or cylinder of breathing gas. This is available only when the tanks used in the dive have been specified by the argument tanklist. The value n should be a valid index for this list (either a serial number in the tank list or a character string matching one of the names in the tank list).

an ascent/descent rate object

created by the functions ascent or descent. This resets the default rate of ascent or descent.

a data frame with 2 columns

containing a dive profile, usually uploaded from a dive computer. The first column should contain the elapsed times, and the second column contains the depths (in metres) measured at these times. The column of elapsed times can be either a character vector containing times in minutes-and-seconds format mm:ss, or an integer vector containing elapsed times in seconds, or a vector of class difftime representing elapsed times in any time unit. In this case you probably want to set the arguments begin=NA and end=NA.

an object of class "dive"

representing a dive profile. This allows the user to paste dive profiles together.

Dives are assumed to start and finish at the surface. This can be changed by specifying values for begin and end. See the section on Start and End of Dive.

Initially the descent rate is set to 30 metres per minute, the ascent rate is 18 metres per minute, and the breathing gas is air. These settings may be changed during the dive by the ... arguments.

A dive object may include periods spent at the surface (depth zero) and may therefore represent a succession of dives separated by surface intervals.

Once an object of class "dive" has been created, it can be plotted and printed (using plot.dive and print.dive). The nitrogen saturation can be computed using haldane and the cumulative oxygen toxicity using oxtox.

Value

An object of class "dive" describing the dive profile and the breathing gases used.

Start and End of Dive

To make it easy to specify simple dive profiles, the algorithm fills in some information. If the diving depths specified in the arguments ... do not start at the surface (depth zero), then by default, the algorithm assumes that the dive did start at the surface, and it adds an extra dive segment at the beginning of the dive. The diver is assumed to descend from the surface, at the standard descent rate, to the first depth specified. Thus dive(c(10,25)) means that the diver will first descend from the surface to 10 metres at a rate of 30 metres per minute, remain there for 25 minutes, then ascend to the surface at a rate of 18 metres per minute.

To change this behaviour, set a different value for the argument begin. If the dive really started at a nonzero depth, e.g. a dry habitat at 3 metres, set begin=3. If one of the arguments ... is a data frame uploaded from a dive computer, then set begin=NA, so that that the dive will start at the first depth specified in this data frame.

Similarly, if the last depth specified by the arguments ... is a depth below the surface (depth greater than zero), then by default the diver is assumed to ascend from this last depth to the surface, at the standard ascent rate. To suppress this altogether, set end=NA. To specify a different final depth for the dive, set a different value for end.

Modifying a dive object

The depths and elapsed times at each waypoint during the dive can be extracted and changed using depths.dive and times.dive.

Dives can be cut into pieces using chop.dive and pasted together using dive.

It is possible to alter the breathing gases used in a dive d, yielding a new dive object. This makes it possible to study the effect of conducting the same dive profile with different breathing gases. You can change the specification of the breathing gas (or gases) by tanklist(d) <- value. In a multiple-tank dive you can change the periods when each tank was used, by whichtank(d) <- value.

Warnings

Not suitable for representing altitude dives.

Author(s)

Adrian Baddeley [e-mail].

See Also

nitrox, ascent, descent, haldane, plot.dive, times.dive, durations.dive, depths.dive, chop.dive, tanklist, whichtank.

Examples

  # Dive to 25 m for 20 min followed by safety stop at 5 metres for 3 min
  d <- dive(c(25,20),c(5,3))
  plot(d)

  # Bounce dive to 20 metres
  d <- dive(20)

  # Two dives separated by a one-hour surface interval
  d <- dive(c(30,15),c(9,2),c(5,5),c(0,60),c(12,60),c(5,5))

  # ASCENT RATES
  # Ascent rate 18 m/min below 9 metres, 6m/min above 9 metres
  d <- dive(c(30, 12), ascent(18), 9, ascent(6), c(5,3))

  # UPLOADED DIVE PROFILE
  data(baron)
  pro <- baron[, 1:2]
  d <- dive(pro)
  d <- dive(pro, begin=NA, end=NA)
  plot(d)

  # GAS USE
  # 30-metre dive on Nitrox 32
  d <- dive(nitrox(0.32), c(30,20), c(5,5))

  # GAS SWITCHING
  # Dive to 18 m for 30 min on air,
  # switch to Nitrox 36, ascend to 5 metres, safety stop
  d <- dive(c(18, 30), nitrox(0.36), c(5,3))
  # Same as above, but ascend to 5 m on air, then switch gas
  d <- dive(c(18, 30), 5, nitrox(0.36), c(5,3))

  # SWITCHING TO SPECIFIC TANKS
  d <- dive(tanklist=list(main=air, deco=nitrox(0.50)),
            tank="main", c(30, 20), 5, tank="deco", c(5,10))

  # Descend to 5 metres on pure oxygen, switch to Trimix,
  # descend to 30 metres, remain 40 minutes, ascend to 6 metres,
  # switch to pure oxygen, ascend to 5 metres, decompress 10 minutes,
  # surface and continue breathing pure oxygen for 10 minutes

  d <- dive(tanklist=list(travel=trimix(0.15, 0.5), deco=nitrox(1)),
            tank="deco", 5, tank="travel", c(30,40), 6, tank="deco",
            c(5,10), c(0,10))