UPsampford             package:sampling             R Documentation

_S_a_m_p_f_o_r_d _s_a_m_p_l_i_n_g

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

     Use Sampford method to select a sample of units (unequal
     probabilities, without replacement, fixed sample size).

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

     UPsampford(pik,eps=1e-6)

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

     pik: vector of prescribed inclusion probabilities.

     eps: the control value, by default equal to 1e-6.

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

     Return a vector (with elements 0 and 1) of size N, where N is the
     population size.   Each element k of this vector indicates the
     status of the unit k  (1, the unit k is selected in the sample; 0,
     otherwise). The value eps is used to control pik (pik>eps & pik <
     1-eps).  The sample size must be small with respect to the 
     population size; otherwise, the selection time can be very long.

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

     Sampford, M. (1967), On sampling without replacement with unequal
     probabilities of selection, _Biometrika_, 54:499-513.

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

     'UPsystematic'

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

     #define the prescribed inclusion probabilities
     pik=c(0.2,0.7,0.8,0.5,0.4,0.4)
     s=UPsampford(pik)
     #the sample is
     (1:length(pik))[s==1]

