Recently, I've run into an issue where the smooth_spline function only offers smoothing levels from 1 to 10, which feels a bit limited for what I need—I’d really like to try more granular settings. I read the related papers and learned that the autosmooth is implemented using Algorithm 642. However, after looking into this method, it doesn’t seem to support stepwise smoothing like the 1–10 scale in smooth_spline. Does anyone know which algorithm package is actually used for smooth_spline with the 1–10 levels? Also, how exactly do these levels correspond to the smoothing factor λ? Is there a specific conversion formula?