Dear All R users, I have many time series. Each of them follows the structure below, x_t = a_0 + a_1 x_{t-1} + a_2 x_{t-2} + \epsilon_t if x_{t-d} < \theta b_0 + b_1 x_{t-1} + b_2 x_{t-2} + \epsilon_t if x_{t-d} >= \theta I hope to classify these series into a few groups. Assume the delay parameter d is same among all the series but the threshold parameters \theta are different. Also the parameters a_i,b_i of the series are same if these series belong to the same group but are different if the series belong to different group. Can you give me some advices in classifying these series by cluster analysis. Thank you in advance. -- Jin