I want to smooth peaks for non-negative matrix factorization (NMF). Since Savitzky-Golay has polynomial smoothing, I think it is good for narrow peak shape in my signal profile. But NMF needs to be non-negative, I wonder I can simply take absolute on Savtizky-Golay filter (or replace negative value with eps (1e-6))? Are there any published applications using only positive range of Savitzky-Golay to smooth data? Or are there other appropriate filter for non-negative data?