07-28-2015 01:02 AM
You can choose Multiplicative Seasonal Exponential Smoothing or Multiplicative Winters method to restrict for positive definite predicts. If you want to see the formulas, please refer to SAS/ETS(R) 9.3 User's Guide.
07-28-2015 09:07 AM
Thank you Ruiwen. I get missing values for all critical values(by default method predicted to be negative)...
Would you be so kind to recommend me some documents about time series predicting methods?
07-28-2015 10:56 AM
This whitepaper might be a good start - even though it discusses automation of forecasting as implemented in SAS Forecast Sever: http://support.sas.com/rnd/app/ets/papers/largescale.pdf
For more details on time series forecasting methods I would suggest to turn to one of the many books available - some of them online and for free, such as: https://www.otexts.org/fpp