Seasonality types

The series frequency, as we saw in the preceding chapters, defines the amounts of intervals in a single cycle unit of the series. The term cycle here refers to constant cycles, and should not be confused with the term cycle component, which was introduced in the previous chapter. In addition, the frequency units are ordered and repeated in the same order. For example, January and December would always be the first and last units, respectively, for a calendric series with a monthly frequency. A seasonal pattern exists in a time series whenever we can tie a repeated event in the series to a specific frequency unit, for example, the average temperature in New York during the month of January, or the average number of passengers in the London underground between 8 a.m. and 9 a.m. Hence, there is a strong relationship between seasonal pattern and the frequency of...