baycheck               package:UsingR               R Documentation

_P_o_p_u_l_a_t_i_o_n _e_s_t_i_m_a_t_e _o_f _t_y_p_e _o_f _B_a_y _C_h_e_c_k_e_r_s_p_o_t _b_u_t_t_e_r_f_l_y

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

     Estimates of the population of a type of Bay Checkerspot butterfly
     near San Francisco.

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

     data(baycheck)

_F_o_r_m_a_t:

     A data frame with 27 observations on the following 2 variables.

     _y_e_a_r a numeric vector

     _N_t estimated number

_S_o_u_r_c_e:

     From chapter 4 of Morris and Doak, _Quantitative Conservation
     Biology: Theory and Practice of Population Viability Analysis_,
     Sinauer Associates, 2003.

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

     data(baycheck)
     plot(Nt ~ year,baycheck)
     ## fit Ricker model N_{t+1} = N_t e^{-rt}W_t
     n = length(baycheck$year)
     yt = with(baycheck,log(Nt[-1]/Nt[-n]))
     nt = with(baycheck,Nt[-n])
     lm(yt ~ nt,baycheck)

