session                 package:secr                 R Documentation

_S_e_s_s_i_o_n _V_e_c_t_o_r

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

     Extract or replace the session names of a 'capthist' object.

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

     session(object, ...)
     session(object) <- value

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

  object: object with 'session' attribute e.g. 'capthist' 

   value: character vector or vector that may be coerced to character,
          one value per session 

     ...: other arguments (not used) 

_D_e_t_a_i_l_s:

     Replacement values will be coerced to character.

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

     a character vector with one value for each session in 'capthist'

_N_o_t_e:

     Like Density, 'secr' uses the term 'session' for a
     closed-population sample. A session usually includes data from
     several closely-spaced capture occasions (often consecutive days).
     Each 'primary session' in the 'robust' design of Pollock (1982)
     would be treated as a session in 'secr'. 'secr' also uses
     'session' for independent subsets of the capture data
     distinguished by characteristics other than sampling time (as
     above). For example, two grids trapped simultaneously could be
     analysed as distinct 'sessions' if (i) they were far enough apart
     that there was negligible prospect of the same animal being caught
     on both grids, and (ii) there was interest in comparing estimates
     from the two grids, or fitting a common detection model.

     The log likelihood for a session model is the sum of the separate
     session log likelihoods. Although this assumes independence of
     sampling, parameters may be shared across sessions, or
     session-specific parameter values may be functions of
     session-level covariates. For many purposes, 'sessions' are
     equivalent to 'groups'. For multi-session models the detector
     array and mask are specified separately for each session. Group
     models are therefore generally simpler to implement. On the other
     hand, sessions offer more flexibility in defining and evaluating
     between-session models, including trend models.

     Sessions are a recent addition to 'secr' and the documentation and
     testing of session capability is therefore less advanced than for
     other features.

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

     Murray Efford murray.efford@otago.ac.nz

_R_e_f_e_r_e_n_c_e_s:

     Pollock, K. H. (1982) A capture-recapture design robust to unequal
     probability of capture. _Journal of Wildlife Management_ *46*,
     752-757.

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

     'capthist'

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

       data(captdata)
       session(captdata)

