function v = horst(t, Y, Z, a, b)
v = zeros(2,1);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
x = Y(1);
y = Y(2);
ylag = Z(:,1);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
dxdt = y;
dydt = a*y*(1-y-b*(x-ylag(1)))-b*y;
v = [dxdt; dydt];