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st: RE: exponential smoothing


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: exponential smoothing
Date   Mon, 16 Aug 2010 18:58:17 +0100

Predicting the logarithm of sales and back-transforming is one possibility. Another is that your sales are fluctuating too erratically to be predictable by this method. 

Nick 
n.j.cox@durham.ac.uk 

Schöler, Lisa


I want to do exponential smoothing for sales with Stata. I used the command

.tssmooth dexponential sales = ussalesdols000, forecast(1)

Sometimes I get negative out of sample forecasts which can't be true for sales. Is there a way to include a constraint so the out of sample forecasts will not get negative?

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