Time series behaviour description

How to describe the sequence of changes of each individual feature?

Let us now concentrate on the individual change pattern of features. Information about each feature consists of a sequence of properties called Time series. Information content of a time series should be carefully considered for the selection of appropriate analysis tools. In the thematic dimension first, as seen before, properties can be measured at nominal level (qualitative data), at ordinal or cardinal level (quantitative data).

Furthermore information content is also concerned by the time dimension:

• At ordinal level: only the order of the sequence is considered. In other words intervals of time (or spacing) are discarded.
• At cardinal level: intervals of time are significant for the analysis.

Originally data can be collected at regular but also at irregular intervals of time. As most techniques for time series analysis require regular intervals, equal spacing procedures should be applied to the original time series prior its analysis.

The following table presents a selection of methods for the analysis of individual time series.