formula.pdMat              package:nlme              R Documentation

_E_x_t_r_a_c_t _p_d_M_a_t _F_o_r_m_u_l_a

_D_e_s_c_r_i_p_t_i_o_n:

     This method function extracts the formula associated with a
     'pdMat' object, in which the column and row names are specified.

_U_s_a_g_e:

     ## S3 method for class 'pdMat':
     formula(x, asList, ...)

_A_r_g_u_m_e_n_t_s:

       x: an object inheriting from class 'pdMat', representing a
          positive definite matrix.

  asList: logical.  Should the asList argument be applied to each of
          the components?  Never used.

     ...: some methods for this generic require additional arguments. 
          None are used in this method.

_V_a_l_u_e:

     if 'x' has a 'formula' attribute, its value is returned, else
     'NULL' is returned.

_N_o_t_e:

     Because factors may be present in 'formula(x)', the 'pdMat' object
     needs to have access to a data frame where the variables named in
     the formula can be evaluated, before it can resolve its row and
     column names from the formula.

_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:

     'pdMat'

_E_x_a_m_p_l_e_s:

     pd1 <- pdSymm(~Sex*age)
     formula(pd1)