R multiple boxplots in one plot-CodePudding

I have a question regarding multiple boxplots. Assume we have data structures like this:

a <- rnorm(100, 0, 1)
b <- rnorm(100, 0, 1)
c <- rbinom(100, 1, 0.5)

My task is to create a boxplot of a and b for each group of c. However, it needs to be in the same plot. Ideally: Boxplot for a and b side by side for group 0 and next to it boxplot for a and b for group 1 and all together in one graphic.

I tried several things, but only the seperate plots are working:

boxplot(a~as.factor(c))
boxplot(b~as.factor(c))

But actually, that's not what I'm searching for. As it has to be one plot.

CodePudding user response：

You can use the tidyverse package for this. You transform your data into long-format that you get three variables: "names", "values" and "group". After that you can plot your boxplots with ggplot():

value_a <- rnorm(100, 0, 1)
value_b <- rnorm(100, 0, 1)
group <- as.factor(rbinom(100, 1, 0.5))

data <- data.frame(value_a,value_b,group)

library(tidyverse)

data %>%
  pivot_longer(value_a:value_b, names_to = "names", values_to = "values") %>%
  ggplot(aes(y = values, x = group, fill = names)) 
  geom_boxplot()

^{Created on 2022-08-19 with}

The at argument controls the grouping and placement of the boxes. Contrary to ggplot2 you need to choose placing manually, but you also get very fine control of spacing very easily.

Slightly refined version of the plot:

boxplot(values ~ ind   c, data = d, at = c(1, 2, 4, 5),
        col = c(2, 4), show.names = FALSE,
        xlab = "")
axis(1, labels= c("c = 0", "c = 1"), at = c(1.5, 4.5))
legend("topright", fill = c(2, 4), legend = c("a", "b"))