How to add text to ggplot below the graph?

Question

I'm looking at figures from Moreira et al. (Nature, 2020) where they have graphs indicating sample size and treatments under the barplots such as this:

Is there a way to reproduce this in ggplot? This would be very useful to indicate all the necessary information regarding an experiment in a compact manner.

Some dummy data for the plot:

library(tidyverse)

tibble(
  Rodent = c(rep("Mouse",11),
             rep("Hamster",7),
             rep("Guinea pig",4),
             rep("Gerbil",12)),
  `Weight (gm)` = rnorm(34,25,10),
  `Long whiskers` = c(rep("+",11),rep("-",7),rep("+",4),rep("-",12)),
  `Long tail` = c(rep("+",11),rep("-",7),rep("+",4),rep("-",12)),
  `Albino or normal` = c(rep("Albino",11),rep("Normal",7),rep("Albino",4),rep("Normal",12))
) %>% 
  ggplot(aes(Rodent,`Weight (gm)`,fill = `Albino or normal`)) +
  geom_boxplot()

stefan · Accepted Answer · 2021-01-13 18:46:30Z

3

There are probably two or three approaches to achieve your desired result. Personally I prefer to do it via patchwork, i.e create a second plot with the additional information you want to display and glue it to your main plot:

library(tidyverse)

d <- tibble(
  Rodent = c(rep("Mouse",11),
             rep("Hamster",7),
             rep("Guinea pig",4),
             rep("Gerbil",12)),
  `Weight (gm)` = rnorm(34,25,10),
  `Long whiskers` = c(rep("+",11),rep("-",7),rep("+",4),rep("-",12)),
  `Long tail` = c(rep("+",11),rep("-",7),rep("+",4),rep("-",12)),
)

p1 <- d %>% 
  ggplot(aes(Rodent,`Weight (gm)`)) +
  geom_boxplot()

d1 <- d %>% 
  select(-`Weight (gm)`) %>%
  count(Rodent, `Long whiskers`, `Long tail`) %>% 
  distinct() %>% 
  mutate(n = as.character(n)) %>% 
  pivot_longer(-Rodent)

p2 <- d1 %>% 
  ggplot(aes(Rodent, fct_rev(name), label = value)) +
  geom_text(size = 10) +
  labs(x = NULL, y = NULL) +
  theme_minimal() +
  theme(panel.grid = element_blank(), axis.text.x = element_blank())

library(patchwork)

p1 / p2

EDIT With a legend on the right it looks like so. I simply added a color legend where I mapped Rodent on color:

p1 <- d %>% 
  ggplot(aes(Rodent,`Weight (gm)`, color = Rodent)) +
  geom_boxplot() +
  theme(legend.position = "right")

p2 <- d1 %>% 
  ggplot(aes(Rodent, fct_rev(name), label = value)) +
  geom_text(size = 10) +
  labs(x = NULL, y = NULL) +
  theme_minimal() +
  theme(panel.grid = element_blank(), axis.text.x = element_blank())

p1 / p2

edited Jan 13, 2021 at 18:46

answered Jan 12, 2021 at 13:39

stefan

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2 Comments

Anurag N. Sharma Over a year ago

Can you please add a possibility of doing the same when the upper plot has a legend on the right side? If there is a legend, the alignment is off!

stefan Over a year ago

Hi Anurag. I just made an edit and added a color legend to the upper plot. Hope I got you right.

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