3 Data Mining and Time Series Berry and Linoff defined data mining as the analysis of huge amounts of data by automatic or semi-automatic means, in order to identify significant patterns or rules [6, 19]. One of the most important data mining techniques is time series analysis. Time series data often arise when monitoring industrial processes or tracking corporate business metrics [22]. Time series analysis can be used to accomplish different goals:
(1).
Descriptive analysis determines what trends and patterns a time series has by plotting or using more complex techniques.
(2).
Spectral analysis is carried out to describe how variation in a time series may be accounted for by cyclic components. This may also be referred to as "Frequency Domain". With this an estimate of the spectrum over a range of frequencies can be obtained and periodic components in a noisy environment can be separated out [23].
(3).
Forecasting can do just that - if a time series has behaved a certain way in the past, the future behavior can be predicted within certain confidence limits by building models.
(4).
Intervention analysis can explain if there is a certain event that occurs that changes a time series. This technique is used a lot of the time in planned experimental analysis.
(5).
Explanative analysis using one or more variable time series, a mechanism that results in a dependent time series can be estimated [11].
One of the most important forecasting techniques is exponential smoothing analysis for time series analysis. Forecasts generated with this method are a weighted average of the past values of the variable. The weights decline for older observations. The rationale is that more recent observations are more inuential than older observations. The exponential smoothing analysis is