suppose I have n+m sample data. I constructs a arima model using first n sample points.
Can I fix the arima model then predict m periods forwardly so as to get the last m predictions. the residuals of the last m sample points are calculated as the difference of the last m real out-sample points and the m predictions.
Having filled the last m residuals,I can do prediction m more forwardly using the m real values and residuals.
as a consequence,when I have new future values,I can do predictions with fixes arima model,but substitutes new future values into the formula.
Is this way workable? Or may cause some problems?