Centers effect matrix so that colMeans(effect) = 0, i.e., for each t, the effect averages to 0 across observations: sum_i f(z_i, t) = 0 for all t. This matches pffr's identifiability constraint for smooth varying coefficient terms.
center_smooth_effect(effect)Centered matrix with same dimensions.
Numeric matrix (n x n_yind) of effect values.