

pdClasses(nlme)                              R Documentation

_P_o_s_i_t_i_v_e_-_D_e_f_i_n_i_t_e _M_a_t_r_i_x _C_l_a_s_s_e_s

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

     Standard classes of positive-definite matrices
     (`pdMat') structures  available in the `nlme' library.

_V_a_l_u_e_:

     Available standard classes:

  pdSymm: general positive-definite matrix, with no addi-
          tional structure

  pdDiag: diagonal

 pdIdent: multiple of an identity

pdCompSymm: compound symmetry structure (constant diagonal
          and constant off-diagonal elements)

pdBlocked: block-diagonal matrix, with diagonal blocks of
          any "atomic" `pdMat' class

pdNatural: general positive-definite matrix in natural
          parametrization (i.e. parametrized in terms of
          standard deviations and correlations). The under-
          lying coefficients are not unrestricted, so this
          class should NOT be used for optimization.

_N_o_t_e_:

     Users may define their own `pdMat' classes by specify-
     ing a `constructor' function and, at a minimum, methods
     for the functions `pdConstruct', `pdMatrix' and `coef'.
     For examples of these functions, see the methods for
     classes `pdSymm' and `pdDiag'.

_A_u_t_h_o_r_(_s_)_:

     Jose Pinheiro and Douglas Bates

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

     `pdCompSymm', `pdDiag', `pdIdent', `pdNatural',
     `pdSymm'

