Probably want a smooth with a sum to zero constraint and a shared smoothing parameter to allow to the global smooth to be adaptive. Also see here for comparisons. Factor-smooth doesn't work because when I did some testing it couldn't accept a global adaptive smoother.
Probably want a smooth with a sum to zero constraint and a shared smoothing parameter to allow to the global smooth to be adaptive. Also see here for comparisons. Factor-smooth doesn't work because when I did some testing it couldn't accept a global adaptive smoother.