lcond.m

用matlab写的一些数值算法

function  y = lcond(L)
% y = L\d, where norm(d,inf) = 1 and norm(y,inf) is maximal

% Version 11.12.2003.  INCBOX

n = size(L,1);
y = -ones(n,1);                              % initialize y
for  i = 2 : n
  si = L(i,1:i-1)*y(1:i-1);
  if  si == 0,  y(i) = -1/L(i,i);
  else,         y(i) = -(sign(si) + si)/L(i,i); end
end