Add Significance Levels to ggplot2 Plot Using ggsignif Package in R (Example Code)

This article explains how to annotate significance levels to a ggplot2 graph in the R programming language.

Setting up the Example

data(iris)                       # Load example data
head(iris)
#   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
# 1          5.1         3.5          1.4         0.2  setosa
# 2          4.9         3.0          1.4         0.2  setosa
# 3          4.7         3.2          1.3         0.2  setosa
# 4          4.6         3.1          1.5         0.2  setosa
# 5          5.0         3.6          1.4         0.2  setosa
# 6          5.4         3.9          1.7         0.4  setosa
install.packages("ggplot2")      # Install & load ggplot2
library("ggplot2")
my_ggplot <- ggplot(iris,        # Drawing a regular ggplot2 boxplot
                  aes(x = Species,
                      y = Sepal.Length)) +
  geom_boxplot()
my_ggplot

r graph figure 1 add significance levels ggplot2 using ggsignif package r

Example: Annotate Significance Levels to ggplot2 Boxplot

install.packages("ggsignif")     # Install & load ggsignif
library("ggsignif")
my_ggplot +                      # Adding significance stars
  geom_signif(comparisons = list(c("setosa", "versicolor"),
                                 c("setosa", "virginica")),
              map_signif_level = TRUE,
              y_position = c(8, 9))

r graph figure 2 add significance levels ggplot2 using ggsignif package r

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