This class is a wrapper around the
formula class. It is not intended for
users to directly manipulate and create new objects.
[formula] The raw formula call
[formula] The translated formula call ready to be evaluated.
[list] List of relevant variables for the evaluation of the different smooths.
Smooth lag variables used for predictions
[charatcer] The response variable in the formula.
[logical] Whether this formula has already been fitted.
mgcv function for defining smooths: s().