R Tutorial
Fundamentals of R
Variables
Input and Output
Decision Making
Control Flow
Functions
Strings
Vectors
Lists
Arrays
Matrices
Factors
DataFrames
Object Oriented Programming
Error Handling
File Handling
Packages in R
Data Interfaces
Data Visualization
Statistics
Machine Learning with R
Adding textual annotations to plots can help clarify data points, indicate specific regions, or add context. In this tutorial, we'll explore how to add text to plots in R using both base graphics and ggplot2.
In base graphics, the primary function for adding text is text().
text():You can add a text label to a specific point in a plot using the text() function:
plot(1:5, 1:5) # Basic scatter plot text(3, 3, "Center") # Adds "Center" at (3,3)
You can use vectors to add multiple labels:
x <- 1:5
y <- 1:5
labels <- c("A", "B", "C", "D", "E")
plot(x, y)
text(x, y, labels, pos=4, offset=0.5, col="red")
pos: Specifies the position of the text relative to the point. It can take values 1 (below), 2 (left), 3 (above), and 4 (right).offset: Specifies the distance between the point and the text.col: Specifies the text color.In ggplot2, the primary function for adding text to a plot is geom_text().
library(ggplot2)
data <- data.frame(x=1:5, y=1:5)
ggplot(data, aes(x, y)) +
geom_point() +
geom_text(aes(label=sprintf("Point %d", 1:5)), vjust=-1)
Here, vjust is used for vertical adjustment. A value of -1 places the text below the points.
ggplot(data, aes(x, y)) +
geom_point() +
annotate("text", x=3, y=3, label=expression(paste(alpha, " = 0.05")), parse=TRUE)
The annotate() function is used here to add a single text annotation. The parse=TRUE argument indicates that the label should be parsed (useful for mathematical notation).
Positioning Text: For precise text positioning, especially to avoid overlapping, you can use the ggrepel package in conjunction with ggplot2. It provides the geom_text_repel() function which helps in auto-adjusting overlapping text labels.
Labeling with Variables: In ggplot2, you can easily label points using a column from your dataframe. Just set aes(label=your_column_name) in geom_text().
Custom Fonts and Sizes: Both text() in base graphics and geom_text() in ggplot2 allow customization of font, size, face, and angle using arguments like cex, fontface, and angle.
Annotating plots with text can enhance clarity and provide important context to the viewer. Whether you're working with base graphics or ggplot2, R offers robust capabilities for textual annotations in visualizations.
R plot add text example:
Adding text annotations to a plot in R using text():
# R plot add text example x <- 1:10 y <- 2 * x + 3 plot(x, y) text(5, 15, "Annotation", col = "red", cex = 1.2)
How to annotate plots in R:
Annotating plots in R using text() for custom annotations:
# How to annotate plots in R x <- 1:10 y <- 2 * x + 3 plot(x, y) text(3, 10, "Custom Annotation", col = "blue", font = 2)
Adding labels to data points in R plot:
Adding labels to specific data points in an R plot using text():
# Adding labels to data points in R plot x <- 1:10 y <- 2 * x + 3 plot(x, y) text(5, 15, labels = "Data Point", col = "green", cex = 1.2)
Customizing text appearance in R plots:
Customizing text appearance in R plots with text():
# Customizing text appearance in R plots x <- 1:10 y <- 2 * x + 3 plot(x, y) text(5, 15, "Custom Text", col = "purple", font = 3, cex = 1.5)
Positioning text in R plot:
Controlling the position of text in an R plot using text():
# Positioning text in R plot x <- 1:10 y <- 2 * x + 3 plot(x, y) text(x = x, y = y, labels = x, pos = 3, col = "orange")
Adding titles and subtitles to R plots:
Adding titles and subtitles to an R plot using title():
# Adding titles and subtitles to R plots x <- 1:10 y <- 2 * x + 3 plot(x, y) title(main = "Main Title", sub = "Subtitle", col.main = "brown", col.sub = "blue")
Annotations with ggplot2 in R: Using ggplot2 for annotations in R plots:
# Annotations with ggplot2 in R
library(ggplot2)
df <- data.frame(x = 1:10, y = 2 * (1:10) + 3)
ggplot(df, aes(x, y)) + geom_point() + annotate("text", x = 5, y = 15, label = "Annotation", color = "red", size = 5)
Rotate text in R plot:
Rotating text in an R plot using text():
# Rotate text in R plot x <- 1:10 y <- 2 * x + 3 plot(x, y) text(5, 15, "Rotated Text", col = "purple", srt = 45)
Adding legend text in R plot:
Adding legend text to an R plot using legend():
# Adding legend text in R plot x <- 1:10 y <- 2 * x + 3 plot(x, y, legend.text = "Legend Text")
Interactive text in R plots:
Adding interactive text to plots using packages like plotly:
# Interactive text in R plots library(plotly) x <- 1:10 y <- 2 * x + 3 plot_ly(x = x, y = y, type = "scatter", mode = "markers+text", text = "Interactive Text")