getGroups.gls              package:nlme              R Documentation

_E_x_t_r_a_c_t _g_l_s _O_b_j_e_c_t _G_r_o_u_p_s

_D_e_s_c_r_i_p_t_i_o_n:

     If present, the grouping factor associated to the correlation
     structure for the linear model represented by 'object' is
     extracted.

_U_s_a_g_e:

     ## S3 method for class 'gls':
     getGroups(object, form, level, data, sep)

_A_r_g_u_m_e_n_t_s:

  object: an object inheriting from class 'gls', representing a
          generalized least squares fitted linear model.

    form: an optional formula with a conditioning expression on its
          right hand side (i.e. an expression involving the '|'
          operator). Defaults to 'formula(object)'.  Not used.

   level: a positive integer vector with the level(s) of grouping to be
          used when multiple nested levels of grouping are present.
          This argument is optional for most methods of this generic
          function and defaults to all levels of nesting.  Not used.

    data: a data frame in which to interpret the variables named in
          'form'. Optional for most methods.  Not used.

     sep: character, the separator to use between group levels when
          multiple levels are collapsed.  The default is ''/''.  Not
          used.

_V_a_l_u_e:

     if the linear model represented by 'object' incorporates a
     correlation structure and the corresponding 'corStruct' object has
     a grouping factor, a vector with the group values is returned;
     else, 'NULL' is returned.

_A_u_t_h_o_r(_s):

     Jose Pinheiro Jose.Pinheiro@pharma.novartis.com and Douglas Bates
     bates@stat.wisc.edu

_S_e_e _A_l_s_o:

     'gls', 'corClasses'

_E_x_a_m_p_l_e_s:

     data(Ovary)
     fm1 <- gls(follicles ~ sin(2*pi*Time) + cos(2*pi*Time), Ovary,
                correlation = corAR1(form = ~ 1 | Mare))
     getGroups(fm1)

