Returns ets model applied to
ets( y, model = "ZZZ", damped = NULL, alpha = NULL, beta = NULL, gamma = NULL, phi = NULL, additive.only = FALSE, lambda = NULL, biasadj = FALSE, lower = c(rep(1e-04, 3), 0.8), upper = c(rep(0.9999, 3), 0.98), opt.crit = c("lik", "amse", "mse", "sigma", "mae"), nmse = 3, bounds = c("both", "usual", "admissible"), ic = c("aicc", "aic", "bic"), restrict = TRUE, allow.multiplicative.trend = FALSE, use.initial.values = FALSE, na.action = c("na.contiguous", "na.interp", "na.fail"), ... )
a numeric vector or time series of class
Usually a three-character string identifying method using the framework terminology of Hyndman et al. (2002) and Hyndman et al. (2008). The first letter denotes the error type ("A", "M" or "Z"); the second letter denotes the trend type ("N","A","M" or "Z"); and the third letter denotes the season type ("N","A","M" or "Z"). In all cases, "N"=none, "A"=additive, "M"=multiplicative and "Z"=automatically selected. So, for example, "ANN" is simple exponential smoothing with additive errors, "MAM" is multiplicative Holt-Winters' method with multiplicative errors, and so on.
It is also possible for the model to be of class
If TRUE, use a damped trend (either additive or
multiplicative). If NULL, both damped and non-damped trends will be tried
and the best model (according to the information criterion
Value of alpha. If NULL, it is estimated.
Value of beta. If NULL, it is estimated.
Value of gamma. If NULL, it is estimated.
Value of phi. If NULL, it is estimated.
If TRUE, will only consider additive models. Default is FALSE.
Box-Cox transformation parameter. If
Use adjusted back-transformed mean for Box-Cox transformations. If transformed data is used to produce forecasts and fitted values, a regular back transformation will result in median forecasts. If biasadj is TRUE, an adjustment will be made to produce mean forecasts and fitted values.
Lower bounds for the parameters (alpha, beta, gamma, phi)
Upper bounds for the parameters (alpha, beta, gamma, phi)
Optimization criterion. One of "mse" (Mean Square Error),
"amse" (Average MSE over first
Number of steps for average multistep MSE (1<=
Type of parameter space to impose:
Information criterion to be used in model selection.
A function which indicates what should happen when the data contains NA values. By default, the largest contiguous portion of the time-series will be used.
Other undocumented arguments.
An object of class "
The generic accessor functions
extract useful features of the value returned by
ets and associated
Based on the classification of methods as described in Hyndman et al (2008).
The methodology is fully automatic. The only required argument for ets is the time series. The model is chosen automatically if not specified. This methodology performed extremely well on the M3-competition data. (See Hyndman, et al, 2002, below.)
Hyndman, R.J., Koehler, A.B., Snyder, R.D., and Grose, S. (2002) "A state space framework for automatic forecasting using exponential smoothing methods", International J. Forecasting, 18(3), 439--454.
Hyndman, R.J., Akram, Md., and Archibald, B. (2008) "The admissible parameter space for exponential smoothing models". Annals of Statistical Mathematics, 60(2), 407--426.
Hyndman, R.J., Koehler, A.B., Ord, J.K., and Snyder, R.D. (2008) Forecasting with exponential smoothing: the state space approach, Springer-Verlag. http://www.exponentialsmoothing.net.
Rob J Hyndman