fems <- fems %>% 
  group_by(CpG) %>% 
  arrange(CpG, AVGMOrder) %>% 
  mutate(Loess = predict(loess(Meth ~ AVGMOrder, span = .5, data=.),
    data.frame(AVGMOrder = seq(min(AVGMOrder), max(AVGMOrder), 1))))