denumerate               package:MASS               R Documentation

_T_r_a_n_s_f_o_r_m _a_n _A_l_l_o_w_a_b_l_e _F_o_r_m_u_l_a _f_o_r `_l_o_g_l_m' _I_n_t_o _O_n_e _F_o_r `_t_e_r_m_s'.

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

     `loglm' allows dimension numbers to be used in place of names in
     the formula.  `denumerate' modifies such a formula into one that
     `terms' can process.

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

     denumerate(x)

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

       x: A formula conforming to the conventions of `loglm', that is,
          it may allow dimension numbers to stand in for names when
          specifying a log-linear model. 

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

     The model fitting function `loglm' fits log-linear models to
     frequency data using iterative proportional scaling.  To specify
     the model the user must nominate the margins in the data that
     remain fixed under the log-linear model.  It is convenient to
     allow the user to use dimension numbers, 1, 2, 3, ... for the
     first, second, third, ..., margins in a similar way to variable
     names.  As the model formula has to be parsed by `terms', which
     treats `1' in a special way and requires parsable variable names,
     these formulae have to be modified by giving genuine names for
     these margin, or dimension numbers.  `denumerate' replaces these
     numbers with names of a special form, namely `n' is replaced by
     `.vn'.  This allows `terms' to parse the formula in the usual way.

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

     A linear model formula like that presented, except that where
     dimension numbers, say `n', have been used to specify fixed
     margins these are replaced by names of the form `.vn' which may be
     processed by `terms'.

_S_i_d_e _E_f_f_e_c_t_s:

     None.

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

     `renumerate'

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

     denumerate(~(1+2+3)^3 + a/b)
     ##  ~ (.v1 + .v2 + .v3)^3 + a/b

