Control Size of ggplot2 Legend Items in R

In this article, we will see how to control the size of ggplot2 Legend Items in R Programming Language. To create an R plot, we use ggplot() function and for making a scatter plot geom_point() function is added to ggplot() function.

Let us first create a regular plot without any modifications so that the difference is apparent.

Example:

# Load Package
library("ggplot2")

# Create a DataFrame 
data <- data.frame(Xdata = rnorm(10),                        
                   Ydata = rnorm(10),
                   LegendData = c("ld-01", "ld-02", "ld-03",
                                  "ld-04", "ld-05", "ld-06",
                                  "ld-07", "ld-08", "ld-09", 
                                  "ld-10"))

# Create a Scatter Plot
ggplot(data, aes(Xdata, Ydata, color = LegendData)) +   
  geom_point()

Output:

To change the Size of Legend, we have to add guides() and guide_legend() functions to the geom_point() function. Inside guides() function, we take parameter color, which calls guide_legend() guide function as value. Inside guide_legend() function, we take an argument called override.aes, which has the list specifying aesthetic parameters of legend keys. Inside this list, we specify the size of legend.

Syntax : guides(...)

Parameter :

• ... : either a string or call to a guide function. here we call guide_legend() guide function.

Return : each scale can be set scale-by-scale

Syntax : guide_legend(override.aes = list())

Parameter :

• override.aes : A list specifying aesthetic parameters of legend key. Inside this list, we specify the size of legend to size object.

Return : Legend Guides for various scales

Example:

# Load Package
library("ggplot2")

# Create a DataFrame 
data <- data.frame(Xdata = rnorm(10),                        
                   Ydata = rnorm(10),
                   LegendData = c("ld-01", "ld-02", "ld-03",
                                  "ld-04", "ld-05", "ld-06",
                                  "ld-07", "ld-08", "ld-09", 
                                  "ld-10"))

# Create a Scatter Plot and change
# the size of legend
ggplot(data, aes(Xdata, Ydata, color = LegendData)) +   
  geom_point()+
  guides(color = guide_legend(override.aes = list(size = 10)))

Output: