Hi all, This is very embarrassment, but I have used some years ago this type of function call: " Arima(trend + max(seasonal), order=c(2,0,1), xreg=fourier(1:n,c*2,m))" Unfortunately, now I'm not able to find the suitable library where this specific fourier-call is implemented. Can you help me to find it? Thanks for your help, Jari