  factor
  Builtin Function



      SSyynnooppssiiss
        Factor a square matrix.

      SSyynnttaaxx
        factor ( _A )

      DDeessccrriippttiioonn
        The factor function computes the LU factorization of the input
        matrix _A. Factor returns a list with 3 elements:

         iiff _A iiss aa ggeenneerraall mmaattrriixx::

        _l_u a matrix containing the LU factors

        _p_v_t
           a vector containing the pivot indices

        _r_c_o_n_d
           the inverse of the condition estimate

        Factor utilizes the LAPACK subroutines DGETRF, DGECON or ZGETRF,
        ZGECON.

         iiff _A iiss aa ssyymmmmeettrriicc mmaattrriixx::

        _l_d_l
           a matrix containing the block diagonal matrix D, and the
           multipliers used to obtain L.

        _p_v_t
           a vector containing the pivot indices

        _r_c_o_n_d
           the inverse of the condition estimate

        Factor utilizes the LAPACK subroutines DSYTRF, DSYCON or ZHETRF,
        ZHECON.

        The user can overide factor's choice of solution type with the
        optional argument TYPE.


          TYPE = "g" or "G"       The general solution is used.



          TYPE = "s" or "S"       the symmetric solution is used.


     Factor returns the results in the above format, so that they may be
     conveniently used with backsub for repetitive solutions. The user-
     function lu will separate the results from factor into separate L
     and U matrices.


     SSeeee AAllssoo
        backsub, inv, lu, solve




