Relative frequencies / proportions with dplyr

Question

Suppose I want to calculate the proportion of different values within each group. For example, using the mtcars data, how do I calculate the relative f

Answer 1

I wrote a small function for this repeating task:

count_pct <- function(df) {
  return(
    df %>%
      tally %>% 
      mutate(n_pct = 100*n/sum(n))
  )
}

I can then use it like:

mtcars %>% 
  group_by(cyl) %>% 
  count_pct

It returns:

# A tibble: 3 x 3
    cyl     n n_pct
    
1     4    11  34.4
2     6     7  21.9
3     8    14  43.8