pdConstruct               package:nlme               R Documentation

_C_o_n_s_t_r_u_c_t _p_d_M_a_t _O_b_j_e_c_t_s

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

     This function is an alternative constructor for the `pdMat' class
     associated with `object' and is mostly used internally in other
     functions. See the documentation on the principal constructor
     function, generally with the same name as the `pdMat' class of
     object.

_U_s_a_g_e:

     pdConstruct(object, value, form, nam, data)

_A_r_g_u_m_e_n_t_s:

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

   value: an optional initialization value, which can be any of the
          following: a `pdMat' object, a positive-definite matrix, a
          one-sided linear formula (with variables separated by `+'), a
          vector of character strings, or a numeric vector. Defaults to
          `numeric(0)', corresponding to an uninitialized object.

    form: an optional one-sided linear formula specifying the
          row/column names for the matrix represented by `object'.
          Because factors may be present in `form', the formula needs
          to be evaluated on a data.frame to resolve the names it
          defines. This argument is ignored when `value' is a one-sided
          formula. Defaults to `NULL'.

     nam: an optional vector of character strings specifying the
          row/column names for the matrix represented by object. It
          must have  length equal to the dimension of the underlying
          positive-definite matrix and unreplicated elements. This
          argument is ignored when `value' is a vector of character
          strings. Defaults to `NULL'.

    data: an optional data frame in which to evaluate the variables
          named in `value' and `form'. It is used to obtain the levels
          for `factors', which affect the dimensions and the row/column
          names of the underlying matrix. If `NULL', no attempt is made
          to obtain information on  `factors' appearing in the
          formulas. Defaults to the parent frame from which the
          function was called.

_V_a_l_u_e:

     a `pdMat' object representing a positive-definite matrix,
     inheriting from the same classes as `object'.

_A_u_t_h_o_r(_s):

     Jose Pinheiro and Douglas Bates

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

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

_E_x_a_m_p_l_e_s:

     pd1 <- pdSymm()
     pdConstruct(pd1, diag(1:4))

