My colleague Udo Sglavo is back, responding to comments on his guest blog from two weeks ago.  For fans of SAS and R, he shows how to incorporate results from Hyndman's R model into SAS. Do the Evolution After publishing my blog on replicating Rob J Hyndman’s  cross validation idea

Look at the following graphs showing one weekly time series. The left hand shows the actual time series plot. To the less statistically inclined this plot might indicate that the data is seasonal due to the troughs during summer and the peaks during winter. However, if you were to use

In this guest blog, my colleague Snurre Jensen (Analytic Solutions Manager, SAS EMEA Technology Practice) discusses a fine point regarding the word “seasonality” in time series forecasting.  When we see general ups and downs in the data that tend to repeat year after year, we commonly refer to this as