If anyone could help me with a time series prob. Attached is a graph of datas.
Could anyone confirm to me if a multiplicative decomposition model wud be appropriate please.
Could you also help me choosing between a simple or a double exponential smoothing method plz.Explanation wud be very much appreciated.ty very muchx...
Thank you guysx
Choice of gains in double exponential smoothing:
This reference suggests these are selected using non-linear least squares using Marquart
(presumably their shorthand for the Levenberg-Marquart algorithm)
My take on this is that you choose them by trial and error.
But given what the gains are used for I would go for (1-gamma) ~ 0.3, and
alpha ~0.2 as a first guess, if that proves unsatisfactory, mabe reduce (1-gamma)
(gamms and alpha are as in the notation of the reference)
than the gains in getting a good result here. In the attached SS I initialse
b1 to the avaerage slope in the data and get reasonable results for quite
wide ranges of alpha and gamma. Try it and see.