Hi, I have a weekly time series in the following format. category Product date Sales Is_Discounted a123 1224 12JUN2016 20 1 a123 1224 19JUN2016 10 0 a123 1224 26JUN2016 25 1 a123 1224 03JUL2016 19 0 a123 1224 10JUL2016 18 0 I need to predict weekly Sales for each unique combination of category and Product. I want to remove the seasonality from this time series and then create forecasts using proc reg and then add the seasonality back on the forecasts. I have been able to create regression model (using month number, week number and Is_Discounted as independent variables) without removing seasonality and its working fine, but I believe the seasonality in the data is impacting my accuracy with regression. I checked proc X12 but I do not understand how to use it to add the seasonality back after regression. Thanks for the help!
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