Time series problems are problems involving a sequence of data points placed in temporal order. We most often represent those data points as a set:
Usually our goal in time series analysis is forecasting; however, there are certainly many other interesting things you can do with a time series that are outside the scope of this book. Forecasting is really just a specialized form of regression, where our goal is to predict some point xt or points 
, given some set of previous points . We can do this when the ...
