In R programming, a time series is a sequence of data points measured evenly over uniform time intervals—typically, monthly or yearly frequencies are used. You can coerce (convert) a standard dataset into a time series using the as.ts function.

For the initial time series, we will use the Fraser River monthly flows (available at http://www.cmu.edu). I couldn't find a source for the dataset, so I copied it from the site to a local file. The data is the monthly flow starting from March 1913. There are over 900 measurements. The data has a definite frequency:

> fraser <- scan("fraser.txt")
Read 946 items

If we look at the data with a standard plot, we don't see...