function osc()
[T,Y] = ode15s(@model,[0:0.5:20],[0.0 0.25 0.0625]);
plot(T,Y(:,1),'o-',T,Y(:,2),'s-',T,Y(:,3),'d-');
xlabel('Time');
ylabel('Exprerssion level');
legend('X_1','X_2','X_3');

function dy = model(t,y)
k=ones(6,1);
dy = zeros(3,1);   
dy(1) =  k(1)* y(2);
dy(2)= -k(2)* y(1) + k(3)* y(2) -  k(4)* y(2)* y(3);
dy(3) = k(5)* y(1)^2 - k(6)* y(3);
