Change Font Size for Annotation using ggplot2 in R

Last Updated : 03 Mar, 2021

ggplot2 is a data visualization package for the statistical programming language R. After analyzing and plotting graphs, we can add an annotation in our graph by annotate() function. This article discusses how the font size of an annotation can be changed with the annotation() function.

Syntax: annotate()

Parameters:

geom : specify text

x : x axis location

y : y axis location

label : custom textual content

color : color of textual content

size : size of text

fontface : fontface of text

angle : angle of text

By adding annotate function with only argument geom=’text’, it shows that ggplot knows that it has to add text, but it needs another parameter such as Location of text (x,y) and text data (label=text).

Approach

Import ggplot2
Create/Import Dataset
Plot the data on a graph
Add annotation() function with required parameters

Let us first create a basic plot without annotating.

Program :

R

# Import Package 
library(ggplot2) 
  
# df dataset 
df <- data.frame(a=c(2,4,8),              
                 b=c(5, 10, 15)) 
  
# plot graph 
plot = ggplot(df, aes(x = a, y = b)) + geom_point() + geom_line() 
  
# output 
plot

Output:

Basic Plot

Now, Let us see how annotation can be added.

Program :

R

# Import Package 
library(ggplot2) 
  
# df dataset 
df <- data.frame(a=c(2,4,8),              
                 b=c(5, 10, 15)) 
  
# plot graph 
plot = ggplot(df, aes(x = a, y = b)) + geom_point() + geom_line() 
  
plot + annotate('text',  
                x = 6, y = 7.5,  
                label = 'GeeksForGeeks', 
                color='darkgreen')

Output:

label & color

To change the size of the text, use the “size” argument. In the below example, the size of GeeksForGeeks is 10 and the color is red.

Program :

R

# Import Package 
library(ggplot2) 
  
# df dataset 
df <- data.frame(a=c(2,4,8),              
                 b=c(5, 10, 15)) 
  
# plot graph 
plot = ggplot(df, aes(x = a, y = b)) + geom_point() + geom_line() 
  
plot + annotate('text', x = 6, y = 7.5,  
                  label = 'GeeksForGeeks', 
                  color='red', 
                  size = 10)

Output:

Size

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