Reordering bars in ggplot barchart

Question

I'm trying to plot a bar chart that shows the R2 value of two variables before and after treatment. I'd like to plot the red bar for "before" first then the blue one for "after" (i.e reverse of the image below)

Example code:

variable = c("stage", "stage", "type", "type")
R2 = c(3.25, 4.21, 5.66,8.90)
treatment = c("before","after", "before", "after")

df <- data.frame(cbind(variable, R2, type))
df$R2 <- as.numeric(df$R2)

p <- ggplot(data = df, aes(x = variable, y = R2, fill=treatment)) + 
  geom_bar(stat = "identity", position = dodge,  color = "black") + 
  scale_fill_manual(values=c("#00BFC4", "#F8766D")) + 
  theme(axis.text = element_text(size=11), axis.title = element_text(size=13))

score 2 · Answer 1 · answered Sep 07 '21 at 21:07

You need to reorder treatment, here is solution with fct_rev

Code

df %>% 
  mutate(treatment = fct_rev(treatment)) %>% 
  ggplot(aes(x = variable, y = R2, fill=treatment)) + 
  geom_bar(stat = "identity", position = "dodge",  color = "black") + 
  scale_fill_manual(values=c("#00BFC4", "#F8766D")) + 
  theme(axis.text = element_text(size=11), axis.title = element_text(size=13))

Output

score 2 · Answer 2 · answered Sep 07 '21 at 21:21

We could use fct_reorder from forcats package (is in tidyverse)

library(tidyverse)
df %>% 
    mutate(R2 = as.numeric(R2),
           treatment = fct_reorder(treatment, R2, min)) %>% 
    ggplot(aes(x = variable, y = R2, fill=treatment)) + 
    geom_col(position = "dodge",  color = "black") + 
    scale_fill_manual(values=c("#00BFC4", "#F8766D")) + 
    theme(axis.text = element_text(size=11), axis.title = element_text(size=13))

Reordering bars in ggplot barchart

2 Answers2

Code

Output