How to Draw Median & Mean Line to Histogram in R (2 Examples)

In this tutorial you’ll learn how to add a vertical mean or median line to a graph in R programming.

Preparing the Examples

data(iris)                     # Loading example data for plot
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

Example 1: Adding Median & Mean to Histogram Using Base R

hist(iris$Sepal.Width)         # Histogram with median line
abline(v = median(iris$Sepal.Width))

r graph figure 1 draw median mean line histogram

hist(iris$Sepal.Width)         # Histogram with mean line
abline(v = mean(iris$Sepal.Width))

r graph figure 2 draw median mean line histogram

Example 2: Adding Median & Mean to Histogram Using ggplot2 Package

install.packages("ggplot2")    # Install ggplot2 package
library("ggplot2")             # Load ggplot2
my_plot <- ggplot(iris,        # Histogram without line
                  aes(Sepal.Width)) +
  geom_histogram()
my_plot

r graph figure 3 draw median mean line histogram

my_plot +                      # Histogram with median line
  geom_vline(xintercept = median(iris$Sepal.Width))

r graph figure 4 draw median mean line histogram

my_plot +                      # Histogram with mean line
  geom_vline(xintercept = mean(iris$Sepal.Width))

r graph figure 5 draw median mean line histogram

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