rucm {rucm}

rucm: Functions to model and predict a time series using Unobserved Components Model

Description

Package rucm contains functions to model and predict a time series using Unobserved Components Model (UCM) (Harvey (1989)) which decomposes the series into its salient components of trend, seasons, cycles, and regression effects due to predictors.

Details

Unobserved Components Models (UCMs) are special cases of more general and powerful tool in time series called State Space Models having an observation equation, which relates the dependent series to an unobserved state vector, and a state equation describing the evolution of the state vector over time. For a detailed discussion on State Space Models refer Harvey (1989) or Helske (2014).

References

Harvey A. (1989). Forecasting, structural time series models and the Kalman filter. Cambridge New York: Cambridge University Press

Helske J (2014). KFAS: Kalman filter and Smoothers for Exponential Family State Space Models. R package version 1.0.4-1, URL http://CRAN.R-project.org/package=KFAS.

SAS Institute Inc (2010). SAS/ETS 9.22 User's Guide. SAS Institute Inc., Cary, NC. URL http://support.sas.com/documentation/cdl/en/etsug/60372/PDF/default/etsug.pdf.

Selukar R (2011). "State Space Modeling Using SAS". Journal of Statistical Software, 41(12), 1-13. URL http://www.jstatsoft.org/v41/i12/.

Petris G, Petrone S (2011). "State Space Models in R". Journal of Statistical Software, 41(4), 1-25. URL http://www.jstatsoft.org/v41/i04/.

Examples

modelNile <- ucm(Nile~0, data = Nile, 
irregular = TRUE, level = TRUE, slope = TRUE)

modelNile #Print the model

#Return smoothed level values
modelNile$s.level 

#Fixing the level variance to an absolute value
modelNile.fix <- ucm(Nile~0, data = Nile, 
irregular = TRUE, level = TRUE, level.var = 500, 
slope = TRUE) 

#Predicting future values of the time series
predict(modelNile.fix, n.ahead = 12)