In R, trying to implement the following filtering logic by group on a large dataset:

Within each group:
If more than one L, keep the lowest L.
If more than one N, keep the highest N.
If both L and N, keep the highest value of N below the lowest L (in addition to lowest L).
Keep all B.

sample data:

dat <- data.frame(group=c("AB","AB","AB","AB","BC","BC","B","B","AD","AD","AD","G"),
type=c("B","L","N","N","N","L","N","N","B","L","L","L"),
value=c(2,4,3,2,5,3,8,9,4,3,9,7))

desired output:

desired_output <- data.frame(group=c("AB","AB","AB","BC","B","AD","AD","G"),
type=c("B","L","N","L","N","B","L","L"),
value=c(2,4,3,3,9,4,3,7))

Looking for a dplyr/tidyr solution. I’ve tried filtering logic after pivot_wider or case_when within filter, but I haven’t even gotten close enough to show any examples. I was expecting this to be simple but applying the logic across columns has me stumped.