codes                  package:base                  R Documentation

_F_a_c_t_o_r _C_o_d_e_s

_D_e_s_c_r_i_p_t_i_o_n:

     This (generic) function returns a numeric coding of a factor. It
     can also be used to assign to a factor using the coded form.

_U_s_a_g_e:

     codes(x)
     codes(x) <- value

_V_a_l_u_e:

     For an ordered factor, it returns the internal coding (1 for the
     lowest group, 2 for the second lowest, etc.).

     For an unordered factor, an alphabetical ordering of the levels is
     assumed, i.e the level that is coded 1 is the one whose name is
     sorted first according to the prevailing collating sequence.
     Warning: the sort order may well depend on the locale, and should
     not be assumed to be ASCII.

_N_o_t_e:

     Normally `codes' is not the appropriate function to use with an
     unordered factor. Use `unclass' or `as.numeric' to extract the
     codes used in the internal representation of the factor, as these
     do not assume that the codes are sorted.

_S_e_e _A_l_s_o:

     `factor', `levels', `nlevels'.

_E_x_a_m_p_l_e_s:

     codes(rep(factor(c(20,10)),3))

     x <- gl(3,5)
     codes(x)[3] <- 2
     x

     data(esoph)
     ( ag <- esoph$alcgp[12:1] )
     codes(ag)

     codes(factor(1:10)) # BEWARE!

