factor.scope              package:stats              R Documentation

_C_o_m_p_u_t_e _A_l_l_o_w_e_d _C_h_a_n_g_e_s _i_n _A_d_d_i_n_g _t_o _o_r _D_r_o_p_p_i_n_g _f_r_o_m _a _F_o_r_m_u_l_a

_D_e_s_c_r_i_p_t_i_o_n:

     'add.scope' and 'drop.scope' compute those terms that can be
     individually added to or dropped from a model while respecting the
     hierarchy of terms.

_U_s_a_g_e:

     add.scope(terms1, terms2)

     drop.scope(terms1, terms2)

     factor.scope(factor, scope)

_A_r_g_u_m_e_n_t_s:

  terms1: the terms or formula for the base model.

  terms2: the terms or formula for the upper ('add.scope') or lower
          ('drop.scope') scope. If missing for 'drop.scope' it is taken
          to be the null formula, so all terms (except any intercept)
          are candidates to be dropped.

  factor: the '"factor"' attribute of the terms of the base object.

   scope: a list with one or both components 'drop' and 'add' giving
          the '"factor"' attribute of the lower and upper scopes
          respectively.

_D_e_t_a_i_l_s:

     'factor.scope' is not intended to be called directly by users.

_V_a_l_u_e:

     For 'add.scope' and 'drop.scope' a character vector of terms
     labels.  For 'factor.scope', a list with components 'drop' and
     'add', character vectors of terms labels.

_S_e_e _A_l_s_o:

     'add1', 'drop1', 'aov', 'lm'

_E_x_a_m_p_l_e_s:

     add.scope( ~ a + b + c + a:b,  ~ (a + b + c)^3)
     # [1] "a:c" "b:c"
     drop.scope( ~ a + b + c + a:b)
     # [1] "c"   "a:b"

