高铁梅老师的《计量经济分析方法与建模》第134页说:“AR(p)模型平稳的充要条件是(多项式的)根全部落在单位圆之外”;
而EViews 5 Users Guide第497页说“If the estimated ARMA process is (covariance) stationary, then all AR roots should lie inside the unit circle.”即根在单位圆之内。
而Guide的第484页说:“The stationarity condition for general AR( ) processes is that the inverted roots of the lag polynomial lie inside the unit circle.”:倒数根在单位圆之内。
请问:平稳性的条件到底是根在圆内还是圆外?到底是根还是倒数根?
[此贴子已经被作者于2008-4-2 18:48:24编辑过]