speed               package:adehabitat               R Documentation

_C_o_m_p_u_t_e_s _t_h_e _S_p_e_e_d _B_e_t_w_e_e_n _S_u_c_c_e_s_s_i_v_e _R_e_l_o_c_a_t_i_o_n_s _o_f _a_n _A_n_i_m_a_l

_D_e_s_c_r_i_p_t_i_o_n:

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

_U_s_a_g_e:

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

_A_r_g_u_m_e_n_t_s:

       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.

_V_a_l_u_e:

     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').

_A_u_t_h_o_r(_s):

     Clment Calenge calenge@biomserv.univ-lyon1.fr

_S_e_e _A_l_s_o:

     'as.traj'

_E_x_a_m_p_l_e_s:

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

