Change Transparency of ggplot2 Plot Legend Items in R (Example Code)

data(iris)                                       # Load and inspect iris 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

data(iris) # Load and inspect iris 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 ggplot2 package
library("ggplot2")                                 # Load ggplot2 package

install.packages("ggplot2") # Install ggplot2 package library("ggplot2") # Load ggplot2 package

my_plot <- ggplot(iris, aes(x = Sepal.Length,    # Default ggplot2 graph
                            y = Sepal.Width,
                            colour = Species)) +
  geom_point()
my_plot                                          # Drawing graph

my_plot <- ggplot(iris, aes(x = Sepal.Length, # Default ggplot2 graph y = Sepal.Width, colour = Species)) + geom_point() my_plot # Drawing graph

my_plot +                                        # Modifying alpha of legend items
  guides(colour = guide_legend(
    override.aes = list(alpha = 0.3)))

my_plot + # Modifying alpha of legend items guides(colour = guide_legend( override.aes = list(alpha = 0.3)))