speed {adehabitat} | R Documentation

## 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`).

### Author(s)

Clément Calenge calenge@biomserv.univ-lyon1.fr

### 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,]

[Package adehabitat version 1.3 Index]