adehabitat (version 1.1-1)

speed: Computes the Speed Between Successive Relocations of an Animal

Description

speed measures the speed between successive relocations of animals, using objects of class traj.

Usage

speed(x, id = levels(x$id), burst = levels(x$burst), date = NULL,
      units = c("seconds", "hours", "days"))

Arguments

x

an object of class traj

id

a character vector giving the identity of the animals for which the speed is to be computed

burst

a character vector giving the identity of the circuits for which the speed is to be computed (see as.traj)

date

a vector of class POSIXct of length 2 (beginning, end) delimiting the period of interest

units

a character string. It determines how the speeds are computed. For example, if the coordinates are given in meters, and if units = "seconds", speeds are returned in meters per second.

Value

• Returns a data frame with the following components:
• id
  the identity of the animal
• x
  if the speed is computed between the relocation 1 and 2, the x coordinate of the relocation 2.
• y
  if the speed is computed between the relocation 1 and 2, the y coordinate of the relocation 2.
• date
  a vector of class POSIXct, giving the date of relocation 2.
• burst
  the identity of the circuit
• sp.x
  the computed speed of the animal in the x direction
• sp.y
  the computed speed of the animal in the y direction
• speed
  the computed speed of the animal on the plane.
• dt
  the duration between the two relocations (in the units given by the parameter units).

See Also

as.traj

Examples

#### Computes the speed for each wild boar
#### monitored at Puechabon
data(puechcirc)
puechcirc
plot(puechcirc)
sp <- speed(puechcirc)
sp[1:4,]