r - ggplot replace count with percentage in geom_bar

Question

I have a dataframe d:

> head(d,20)
   groupchange Symscore3
1            4         1
2            4         2
3            4         1
4            4         2
5            5         0
6            5         0
7            5         0
8            4         0
9            2         2
10           5         0
11           5         0
12           5         1
13           5         0
14           4         1
15           5         1
16           1         0
17           4         0
18           1         1
19           5         0
20           4         0

That I am plotting with:

ggplot(d, aes(groupchange, y=..count../sum(..count..),  fill=Symscore3)) +
  geom_bar(position = "dodge") 

In this way each bar represents its percentage on the whole data.

Instead I would like that each bar represents a relative percentage; i.e. the sum of the bar in obtained with groupchange = k should be 1.

Answer 1

First summarise and transform your data:

library(dplyr)
d2 <- d %>% 
  group_by(groupchange, Symscore3) %>% 
  summarise(count = n()) %>% 
  mutate(perc = count/sum(count))

Then you can plot it:

ggplot(d2, aes(x = factor(groupchange), y = perc*100, fill = factor(Symscore3))) +
  geom_bar(stat="identity", width = 0.7) +
  labs(x = "Groupchange", y = "percent", fill = "Symscore") +
  theme_minimal(base_size = 14)

this gives:

---

Alternatively, you can use the percent function from the scales package:

brks <- c(0, 0.25, 0.5, 0.75, 1)

ggplot(d2, aes(x = factor(groupchange), y = perc, fill = factor(Symscore3))) +
  geom_bar(stat="identity", width = 0.7) +
  scale_y_continuous(breaks = brks, labels = scales::percent(brks)) +
  labs(x = "Groupchange", y = NULL, fill = "Symscore") +
  theme_minimal(base_size = 14)

which gives: