function dydt = kepler_ode2Y(t,Y)
% assume 'Y' is a vector of form y = [ x ;  y ;z]
global rho sigma beta
%rho = 28;


x = Y(1);
y = Y(2);
z = Y(3);

dydt = -x*z + rho * x - y;

dydt = [0 ; dydt; 0];


        
