dplyr - filter by group size

Question

What is the best way to filter a data.frame to only get groups of say size 5?

So my data looks as follows:

require(dplyr)
n <- 1e5
x <- rnorm(n         


        

Answer 1

I know you asked for a dplyr solution but if you combine it with some purrr you can get it in one line without specifying any new functions. (A little slower though.)

library(dplyr)
library(purrr)
library(tidyr)

dat %>% 
  group_by(cat) %>% 
  nest() %>% 
  mutate(n = map(data, n_distinct)) %>%
  unnest(n = n) %>% 
  filter(n == 5) %>% 
  select(cat, n)