1function [L,U,P] = lu_left (A) 2%LU_LEFT left-looking LU factorization. 3% Example: 4% [L,U,P] = lu_left (A) 5% See also: cs_demo 6 7% Copyright 2006-2012, Timothy A. Davis, http://www.suitesparse.com 8 9n = size (A,1) ; 10P = eye (n) ; 11L = zeros (n) ; 12U = zeros (n) ; 13for k = 1:n 14 x = [ L(:,1:k-1) [ zeros(k-1,n-k+1) ; eye(n-k+1) ]] \ (P * A (:,k)) ; 15 U (1:k-1,k) = x (1:k-1) ; % the column of U 16 [a i] = max (abs (x (k:n))) ; % find the pivot row i 17 i = i + k - 1 ; 18 L ([i k],:) = L ([k i], :) ; % swap rows i and k of L, P, and x 19 P ([i k],:) = P ([k i], :) ; 20 x ([i k]) = x ([k i]) ; 21 U (k,k) = x (k) ; 22 L (k,k) = 1 ; 23 L (k+1:n,k) = x (k+1:n) / x (k) ; % divide the pivot column by U(k,k) 24end 25