15.2 Time-varying seasonality and amplitude
If \(\beta_1\) and \(\beta_2\) vary in time then the seasonal cycle also varies in time. Let’s imagine that \(\beta_1\) varies from -1 to 1 over our 100 time steps while \(\beta_2\) varies from 1 to -1.
So the seasonal cycle flips between the start and end of our time series.
A time series simulated with that flip looks like so: