Regularized time-varying ODE coefficients of SEI dynamic equation for the Canadian measles incidence data (Li, Zhu, Wang, 2015). Left panel: time-varying ODE coefficient curve that reflects both yearly and seasonal effects with the regularized yearly effect (red curve) embedded; right panel: regularized (red curve), non-regularized (blue) and two-year local constant (circles) estimates of yearly effects. The new regularized method shows that the yearly effect is relatively large in the early years and deceases gradually to a constant after 1958.