An email I received today: I have a small problem. I have a time series called x : If I use the default values of auto.arima(x), the best model is an ARIMA(1,0,0) However, I tried the function ndiffs(x, test=“adf”) and ndiffs(x, test=“kpss”) as the KPSS test seems to be the default value, and the number of difference is 0 for the kpss test (consistent with the results of …