Change order of boxplots in tidy dataframe with geom_boxplot()

Question

I have a data that looks like this:

cats = c("cat1", "cat2", "cat3", "cat4")
df = data.frame(a = rnorm(100), b = as.factor(rep(cats, 25)))

When I plot it I get something like this: ggplot(data = df) + geom_boxplot(aes(x = b, y = a, fill = b))

But what can I do if I'd like them to be in the order cat4, cat3, cat2, cat1 on the x-axis. Or even in a completely different order?

Change the order of the levels, e.g. using forcats::fct_rev(b) will reverse the order or use `factor(b, levels = c("cat2", "cat4", ..))` — stefan, Aug 27 '20 at 11:32
Depending on what you want to do, you can use `reorder`, `relevel` or re-specify the "order" with `factor` — Vincent Guillemot, Aug 27 '20 at 11:33
You can also use `xlim` such as `p + xlim("cat4","cat3","cat2","cat1")` — Paul Endymion, Aug 27 '20 at 11:43
And if you just want to reverse the order on the axis: `+ scale_x_reverse()` — Ben Norris, Aug 27 '20 at 11:49
Does this answer your question? [Order and color of bars in ggplot2 barplot](https://stackoverflow.com/questions/17331892/order-and-color-of-bars-in-ggplot2-barplot) — chemdork123, Aug 27 '20 at 15:34

score 1 · Answer 1 · answered Aug 27 '20 at 16:57

It is not mandatory to define the variable as.factor() for ggplot. By default it will recode the variable as.factor, but in this case it will follow the alphabetic order.

However if you want a particular order, you need to define as.factor() and enter the order of the levels.

For example, if you want the boxplots ordered according to their median values:

cats = c("cat1", "cat2", "cat3", "cat4")
df = tibble(a = rnorm(100), b = rep(cats, 25))

library(dplyr)
position <- df %>% group_by(b) %>% summarise(median=median(a)) %>% 
  arrange(desc(median)) %>% pull(b)

df$b <- factor(df$b,levels=position)
# order_wanted <- c(2,1,4,3)
# levels(df$b) <- paste0("cat",order_wanted)

library(ggplot2)
ggplot(data = df) + geom_boxplot(aes(x = b, y = a, fill = b))

Change order of boxplots in tidy dataframe with geom_boxplot()

1 Answers1