To add a custom model for ARIMA forecasting:
Follow steps 1 and 2 in Using ARIMA Custom Models.
In the Add ARIMA Model dialog, indicate the orders for each parameter of the non-seasonal and, optionally, seasonal model, and then click OK.
Follow these rules for entering model orders:
Non-seasonal component orders can be 0 to 10. Seasonal component orders can be 0 to 2.
Orders must be integers.
At least one parameter of the non-seasonal or seasonal model component must be non-zero.
As with standard ARIMA notation, the p portion of the model definition goes in the AR box, the q portion in the MA box, and the d portion in the I box.
The time-period portion of a seasonal model is taken from the existing Predictor information for that series but is not included in the Custom models list.
When the definition is complete, click OK.
The new model is displayed in the Custom models list. Seasonal models are preceded by S—SARIMA(2,0,3)(1,0,2), for example.