Discrete time models
Discrete time models, such as the ones we have been looking at so far, separate time into slices at regular intervals. For us to be able to predict future values of time slices, we assume that they are dependent on past slices.
Time series can also be analyzed with respect to frequency rather than time. We won't discuss frequency domain analysis in this chapter but the book's wiki at http://wiki.clojuredatascience.com contains links to further resources.
In the following, let yt denote the value of an observation at time t. The simplest time series possible would be one where the value of each time slice is the same as the one directly preceding it. The predictor for such a series would be:
This is to say that the prediction ...