%LU     LU factorization.
%   [L,U] = LU(X) stores an upper triangular matrix in U and a
%   "psychologically lower triangular matrix" (i.e. a product
%   of lower triangular and permutation matrices) in L, so
%   that X = L*U.  X must be square.
%
%   [L,U,P] = LU(X) returns lower triangular matrix L, upper
%   triangular matrix U, and permutation matrix P so that
%   P*X = L*U.
%
%   LU(X), with one output argument, returns the output from
%   LAPACK'S DGETRF or ZGETRF routine.
%
%   LU(X,THRESH) controls pivoting in sparse matrices, where
%   THRESH is a pivot threshold in [0,1].  Pivoting occurs
%   when the diagonal entry in a column has magnitude less than
%   THRESH times the magnitude of any sub-diagonal entry in that
%   column.  THRESH = 0 forces diagonal pivoting.  THRESH = 1 is
%   the default.
%
%   See also LUINC, QR, RREF.

%   Copyright 1984-2000 The MathWorks, Inc. 
%   $Revision: 5.14 $  $Date: 2000/06/01 02:04:16 $
%   Built-in function.

