I have the following result from using
auto.arima which includes an SMA term. I would like to hand calculate using the coefficients to get the value of 786.1291812. I am unsure, however, about how to use the SMA term.
Series: ts_train Regression with ARIMA(3,0,1)(0,1,1) errors Coefficients: ar1 ar2 ar3 ma1 sma1 0.8919 0.1849 -0.3847 -0.6419 -0.6783 s.e. 0.1072 0.0917 0.0680 0.0990 0.0847
In Excel, I have the following:
$$=JAN2017+(AR1*(DEC2017-DEC2016))+(AR2*(NOV2017-NOV2016))+(AR3*(OCT2017-OCT2016))+(MA1*(DEC2017actual - DEC2017fitted)) + (SMA?) $$