library(tidyverse)
data(diamonds)


getPercentages <- function(df, colName) {
  var=rlang::quo_squash(rlang::enquo(colName))
  colName=rlang::quo_name(var)

  df.cnt <- df %>% select(!!var) %>%
    table() %>%
    as.data.frame() %>%
    rename(!!colName :=1, Freq=2) %>%
    mutate(Perc=100*Freq/sum(Freq))
}

diamonds %>% getPercentages(cut)

df=diamonds %>% group_by(cut) %>% group_map(~.x %>% getPercentages(clarity))
ggplot(df,aes(x=clarity,y=Perc))+geom_col()+facet_wrap(~cut)