dplyr - Group by and select TOP x %

Question

Using the package dplyr and the function sample_frac it is possible to sample a percentage from every group. What I need is to first sort the elements in every

Answer 1

Here's another way

mtcars %>% 
  select(gear, wt) %>% 
  arrange(gear, desc(wt)) %>% 
  group_by(gear) %>% 
  slice(seq(n()*.2))

   gear    wt
  (dbl) (dbl)
1     3 5.424
2     3 5.345
3     3 5.250
4     4 3.440
5     4 3.440
6     5 3.570

I take "top" to mean "having the highest value for wt" and so used desc().