
function vfield = lorenz(orbit)
s = 10; b = 8/3; r = 28;
vfield = zeros(size(orbit));
x = orbit(1,:);
y = orbit(2,:);
z = orbit(3,:);
vfield(1,:) = s*(y-x);
vfield(2,:) = r*x - y - x.*z;
vfield(3,:) = x.*y - b*z;  