4.6 Exercises

1. Write a function to compute the mean and standard deviation of a time series, and apply it to the PBS data. Plot the series with the highest mean, and the series with the lowest standard deviation.

2. Use GGally::ggpairs() to look at the relationships between the STL-based features for the holiday series in the tourism data. Change seasonal_peak_year and seasonal_trough_year to factors, as shown in Figure 4.3. Which is the peak quarter for holidays in each state?

3. Use a feature-based approach to look for outlying series in the PBS data. What is unusual about the series you identify as “outliers”.