function vprime = Vallisode(t,vin)

global b;
global c;
global xstar;


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

% compute derivatives with the Lorenz model
xprime =b*y - c*(x-xstar);
yprime = x*z - y;
zprime = -x*y - (z-1);

% map back to vector format
vprime=[xprime;yprime;zprime];

end