ABSTRACT
Time series have played a role in several of the earlier chapters. In particular, environmental monitoring (Chapter 5) usually involves collecting observations over time at some xed sites, so that there is a time series for each of these sites, and the same is true for impact assessment (Chapter 6). However, the emphasis in the present chapter will be different, because the situations that will be considered are where there is a single time series, which may be reasonably long (say with 50 or more observations), and the primary concern will often be to understand the structure of the series.
