Given two columns with the same name how can I plot two boxplots side by side over the same name in R?

Question

I have a problem with ggplot. Assuming I have the dataframe 'df_temp' I would like to plot the boxplots for the 7 columns. However, the second and third columns have the same name 'B'. How can I have a plot where on the x-axis at the letter 'B' I have two boxplots (related to the second and third columns)? I attach the code for a toy example. Thanks to anyone who can help me out!

df_temp <- data.frame(
  A = c(0.206, 0.192, 0.187, 0.213, 0.167, 0.209, 0.213, 0.155, 0.190, 0.192),
  B = c(0.260, 0.210, 0.215, 0.280, 0.271, 0.230, 0.232, 0.238, 0.220, 0.278),
  B = c(0.185, 0.276, 0.233, 0.225, 0.239, 0.242, 0.231, 0.195, 0.198, 0.200),
  C = c(0.204, 0.246, 0.212, 0.252, 0.209, 0.244, 0.206, 0.212, 0.210, 0.276),
  D = c(0.218, 0.201, 0.230, 0.189, 0.241, 0.193, 0.225, 0.198, 0.239, 0.199),
  E  = c(0.275, 0.268, 0.257, 0.273, 0.258, 0.262, 0.210, 0.274, 0.285, 0.306),
  F  = c(0.234, 0.239, 0.213, 0.233, 0.250, 0.217, 0.253, 0.217, 0.277, 0.221))

library(reshape2)
df_long <- melt(df_temp)

library(ggplot2)
ggplot(data = df_long, aes(x = variable, y = value)) + 
  geom_boxplot(width = 0.5, outliers = FALSE) +
  ylab("Value") +
  theme_minimal() +
  theme(axis.text.x = element_text(angle = 0, hjust = 0.5, size = 12), text = element_text(size = 14)) +
  theme(axis.text.y = element_text(angle = 0, hjust = 0.5, size = 12)) +
  theme(plot.title = element_text(hjust = 0.5)) +
  theme(axis.text.x = element_blank(), axis.ticks.x = element_blank(), axis.title.x = element_blank()) +
  theme(axis.text.x = element_text(size = 12, angle = 90, hjust = 0.5)) +
  coord_cartesian(ylim = c(0.17, 0.45))

jpsmith · Accepted Answer · 2024-09-09 18:20:36Z

A simple/quick-and-dirty way would be to just rename one column B with a blank space behind it:

df_temp <- data.frame(
  A = c(0.206, 0.192, 0.187, 0.213, 0.167, 0.209, 0.213, 0.155, 0.190, 0.192),
  B = c(0.260, 0.210, 0.215, 0.280, 0.271, 0.230, 0.232, 0.238, 0.220, 0.278),
  B = c(0.185, 0.276, 0.233, 0.225, 0.239, 0.242, 0.231, 0.195, 0.198, 0.200),
  C = c(0.204, 0.246, 0.212, 0.252, 0.209, 0.244, 0.206, 0.212, 0.210, 0.276),
  D = c(0.218, 0.201, 0.230, 0.189, 0.241, 0.193, 0.225, 0.198, 0.239, 0.199),
  E  = c(0.275, 0.268, 0.257, 0.273, 0.258, 0.262, 0.210, 0.274, 0.285, 0.306),
  F  = c(0.234, 0.239, 0.213, 0.233, 0.250, 0.217, 0.253, 0.217, 0.277, 0.221))

names(df_temp)[3] <- "B "

df_long <- reshape2::melt(df_temp)

Your ggplot code then outputs:

It may be better to look "upstream" and see what's causing the names to be the same. In R, it is very uncommon for that to be the case - even in the sample data you provided, it will not name them the same (it creates B and B.1 named columns).

Jon Spring · Accepted Answer · 2024-09-09 18:29:50Z

1

Or if you want the two "B" columns to appear in the same x position, you could assign them to the same x variable, while keeping them in different groups.

df_long <- melt(df_temp) |> 
  transmute(x_var = ifelse(variable == "B.1", "B", as.character(variable)),
            variable, value)

library(ggplot2)
ggplot(data = df_long, aes(x = x_var, y = value, group = variable)) + 
...

answered Sep 9, 2024 at 18:29

Jon Spring

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