Types of pattern
A few patterns in time series are particularly important.
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Most time series show more than one of these patterns to some degree.
World rice production
The time series plot below shows the total world rice production each year from 1961 to 2001.
The dominant feature of this time series is the upward trend over the period.
Tourist arrivals in Fiji
This time series shows the total number of tourists arriving in Fiji each month between January 2004 and December 2007.
Tourist arrivals are highly seasonal. In most tourist destinations, there is a single peak in the summer of each year but in Fiji, the peak is in the winter months of July to September which have less rainfall and are cooler. This is a seasonal pattern.
US defence expenditure
The time series below shows the investment in defence in the USA between 1947 and 2006, with all values reported in '2000 dollars'.
The 'wavy' appearance indicates autocorrelation — if there is high expenditure in one year, there is usually high expenditure in the adjacent years too.
British Airways share volumes traded
The final example shows the number of British Airways shares that were traded in each of the first 57 trading days of 2002 — between 2nd January and 21st March.
This time series is dominated by random fluctuations — the volume of shares traded seems to vary unpredictably.