文件名称：Arima 模型 外文文献
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更新时间：2021-05-24 09:20:08
ARIMA
We show that a stationary ARMA(p, q) process {Xn, n = 0, 1, 2, •••} whose moving-average polynomial has a root on the unit circle cannot be embedded in any continuous-time autoregressive moving-average (ARMA) process {7(t), t ^ 0}, i.e. we show that it is impossible to find a continuous-time ARMA process {7(t)} whose autocovariance function at integer lags coincides with that of {Xn}. This provides an answer to the previously unresolved question raised in the papers of Chan and Tong (J Time Ser. Anal. 8 (1987), 277-81), He and Wang (J Time Ser. Anal. 10 (1989), 315-23) and Brockwell (J. Time Ser. Anal. 16 (1995), 451—60).