These special functions provide interfaces to more complicated functions within the model formulae interface.
common_xregs
The trend special includes common linear trend regressors in the model. It also supports piecewise linear trend via the knots argument.
trend(knots = NULL, origin = NULL)
knots | A vector of times (same class as the data's time index) identifying the position of knots for a piecewise linear trend. |
origin | An optional time value to act as the starting time for the trend. |
The season special includes seasonal dummy variables in the model.
season(period = NULL)
period | The periodic nature of the seasonality. This can be either a number indicating the number of observations in each seasonal period, or text to indicate the duration of the seasonal window (for example, annual seasonality would be "1 year"). |
The fourier special includes seasonal fourier terms in the model. The maximum order of the fourier terms must be specified using K.
fourier(period = NULL, K, origin = NULL)
period | The periodic nature of the seasonality. This can be either a number indicating the number of observations in each seasonal period, or text to indicate the duration of the seasonal window (for example, annual seasonality would be "1 year"). |
K | The maximum order of the fourier terms. |
origin | An optional time value to act as the starting time for the fourier series. |