4.1 Some simple statistics

Any numerical summary computed from a time series is a feature of that time series — the mean, minimum or maximum, for example.

The features can be computed using the features() function. For example, let’s compute the means of all the series in the Australian tourism data.

The new column V1 contains the mean of each time series.

It is useful to give the resulting feature columns names to help us remember where they came from. This can be done by using a list of functions.

Here we see that the series with least average number of visits was “Other” visits to Kangaroo Island in South Australia.

Rather than compute one feature at a time, it is convenient to compute many features at once. A common short summary of a data set is to compute five summary statistics: the minimum, first quartile, median, third quartile and maximum. These divide the data into four equal-size sections, each containing 25% of the data. The quantile() function can be used to compute them.

Here the minimum is labelled 0% and the maximum is labelled 100%.