getCovariate.varFunc          package:nlme          R Documentation

_E_x_t_r_a_c_t _v_a_r_F_u_n_c _C_o_v_a_r_i_a_t_e

_D_e_s_c_r_i_p_t_i_o_n:

     This method function extracts the covariate(s) associated with the
     variance function represented by 'object', if any is present.

_U_s_a_g_e:

     ## S3 method for class 'varFunc':
     getCovariate(object, form, data)

_A_r_g_u_m_e_n_t_s:

  object: an object inheriting from class 'varFunc', representing a
          variance function structure.

    form: an optional formula specifying the covariate to be evaluated
          in 'object'. Defaults to 'formula(object)'.

    data: some methods for this generic require a 'data' object.  Not
          used in this method.

_V_a_l_u_e:

     if 'object' has a 'covariate' attribute, its value 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:

     'covariate<-.varFunc'

_E_x_a_m_p_l_e_s:

     vf1 <- varPower(1.1, form = ~age)
     covariate(vf1) <- Orthodont[["age"]]
     getCovariate(vf1)