htseg1: Simple examples of hierarchical time series.
Description
These are simulated data. htseg1 has three levels with a total of 8
series each of length 10. htseg2 has four levels with a total of 17
series each of length 16.
R. J. Hyndman, R. A. Ahmed, G. Athanasopoulos and H.L. Shang
(2011) Optimal combination forecasts for hierarchical time series.
Computational Statistics and Data Analysis, 55(9), 2579--2589.
http://robjhyndman.com/papers/hierarchical/