function d=Lrnz(t,y)
% Lrnz(t,y) evaluates the vector field for the Lorenz system; 
% see Example 17.4 of Hale & Kocak. parameter=[s,r,b] (global).

global parameter
d=[parameter(1)*(y(2)-y(1));parameter(2)*y(1)-y(2)-y(1)*y(3);y(1)*y(2)-parameter(3)*y(3)];
% M. Day May 8, 2012