How to use stat="count" to label a bar chart with counts or percentages in ggplot2?

Question

I'm trying to produce a stacked column chart with data labels.

I'm able to produce the chart, but was unable to find a way to input data labels. I have tried geom_text() but it keeps asking me to input a y label (which if you see the ggplot code is not there). I have also tried adding geom_text(stat = "count") but that also gives me an error saying

"Error: geom_text requires the following missing aesthetics: y and label".

PS - i'm aware I need to rename the y axis as percentage. I'm also trying to figure out how to have more contrasting colours

ggplot(property,
       aes(x=Bedrooms.New, fill=Property.Type.)) + 
  geom_bar(position = "fill") + 
  scale_x_discrete(name = "Number of Bedrooms", 
                   limits = sort(factor(unique(property$Bedrooms.New))))

I have added an image below to see what my output is right now!

Answer 1

As the error message is telling you, geom_text requires the label aes. In your case you want to label the bars with a variable which is not part of your dataset but instead computed by stat="count", i.e. stat_count.

The computed variable can be accessed via ..NAME_OF_COMPUTED_VARIABLE... , e.g. to get the counts use ..count.. as variable name. BTW: A list of the computed variables can be found on the help package of the stat or geom, e.g. ?stat_count

UPDATE: The dot-dot notation was deprecated in ggplot2 3.4.0. Instead we could or should use after_stat, i.e. use e.g. after_stat(count) instead of ..count..

Using mtcars as an example dataset you can label a geom_bar like so:

library(ggplot2)

ggplot(mtcars, aes(cyl, fill = factor(gear)))+
  geom_bar(position = "fill") +
  geom_text(aes(label = after_stat(count)), stat = "count", position = "fill")

Two more notes:

1. To get the position of the labels right you have to set the position argument to match the one used in geom_bar, e.g. position="fill" in your case.

2. While counts are pretty easy, labelling with percentages is a different issue. By default stat_count computes percentages by group, e.g. by the groups set via the fill aes. These can be accessed via after_stat(prop). If you want the percentages to be computed differently, you have to do it manually.

As an example if you want the percentages to sum to 100% per bar this could be achieved like so:

library(ggplot2)

ggplot(mtcars, aes(cyl, fill = factor(gear))) +
  geom_bar(position = "fill") +
  geom_text(
    aes(label = after_stat(
      count / tapply(count, x, sum)[as.character(x)]
    )),
    stat = "count", position = "fill"
  )

Answer 2

Adding a follow-up to the answer above, since this answer usually gets me 90% of the way, but I can never remember how to also:

• center the labels (position_fill(vjust = 0.5))
• make the percent labels pretty (scales::percent())

library(ggplot)

ggplot(mtcars, aes(cyl, fill = factor(gear)))+
  geom_bar(position = "fill") +
  geom_text(aes(label = scales::percent(..count.. / tapply(..count.., ..x.., sum)[as.character(..x..)])), stat = "count", position = position_fill(vjust = 0.5))

And here's an alternative with pre-calculations in advance:

mtcars %>% 
  count(gear, cyl) %>% 
  group_by(cyl) %>% 
  mutate(perc = n / sum(n)) %>% 
  ggplot(aes(cyl, perc, fill = factor(gear)))+
  geom_col(position = "fill") +
  geom_text(aes(label = scales::percent(perc)), position = position_fill(vjust = 0.5))