Extend contigency table with proportions (percentages)

Question

I have a contingency table of counts, and I want to extend it with corresponding proportions of each group.

Some sample data (tips data set from gg

Answer 1

Here's a tidyverse version:

library(tidyverse)
data(diamonds)

(as.data.frame(table(diamonds$cut)) %>% rename(Count=1,Freq=2) %>% mutate(Perc=100*Freq/sum(Freq)))

Or if you want a handy function:

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

Now you can do:

diamonds %>% getPercentages(cut)

or this:

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