sample                 package:base                 R Documentation

_R_a_n_d_o_m _S_a_m_p_l_e_s _a_n_d _P_e_r_m_u_t_a_t_i_o_n_s

_D_e_s_c_r_i_p_t_i_o_n:

     `sample' takes a sample of the specified size from the elements of
     `x' using either with or without replacement.

_U_s_a_g_e:

     sample(x, size, replace=FALSE, prob)

_A_r_g_u_m_e_n_t_s:

       x: Either a (numeric, complex, character or logical) vector of
          more than one element from which to choose, or a positive
          integer.

    size: A positive integer giving the number of items to choose.

 replace: Should sampling be with replacement?

    prob: A vector of probabilities of obtaining the elements of the
          vector being sampled.

_D_e_t_a_i_l_s:

     If `x' has length 1, sampling takes place from `1:x'.

     By default `size' is equal to `length(x)' so that `sample(x)'
     generates a random permutation of the elements of `x' (or `1:x').

     The optional `prob' argument can be used to give a vector of
     probabilities of obtaining the elements of the vector being
     sampled. If `replace' is false, these probabilities are applied
     sequentially, that is the probability of choosing the next item is
     proportional to the probabilities amongst the remaining items.

_E_x_a_m_p_l_e_s:

     x <- 1:12
     # a random permutation
     sample(x)
     # bootstrap sampling
     sample(x,replace=TRUE)

     # 100 Bernoulli trials
     sample(c(0,1), 100, replace = TRUE)

