In this tutorial, we learn to add text annotations to plots using the text() and mtext() functions from the Graphics package.

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dataCrunch Data Visualization With R
Learn To Add Text Annotations To Plots

2. dataCrunch
Text Annotations
Slide 2

3. dataCrunchText Annotations: Objectives
Slide 3
In this section, we will learn to:
Add text annotations to the plots using
● text() function
● mtext() function

4. dataCrunchText Annotations: Introduction
Slide 4
The text() and the mtext() functions allow the user to add text annotations to the plots. While the
text() function places the text inside the plot, the mtext() function places the text on the margins of
the plot.
Below is the syntax for both the functions:
# the text function
text(x, y = NULL, labels = seq_along(x), adj = NULL,
pos = NULL, offset = 0.5, vfont = NULL,
cex = 1, col = NULL, font = NULL, ...)
# the mtext function
mtext(text, side = 3, line = 0, outer = FALSE, at = NA,
adj = NA, padj = NA, cex = NA, col = NA, font = NA, ...)
Let us explore each function and its arguments one by one:

5. dataCrunchText Annotations: text()
Slide 5
To add text annotations using the text() function, the following 3 arguments must be supplied:
● x: x axis coordinate
● y: y axis coordinate
● text: the text to be added to the plot
Below is a simple example:
# create a basic plot
plot(mtcars$disp, mtcars$mpg)
# add text
text(340, 30, "Sample Text")
The text appears at the coordinates (340, 30) on the
plot. Ensure that the text is enclosed in double quotes
and the coordinates provided are within the range of
the X and Y axis variable.

6. dataCrunchtext(): Color
Slide 6
# create a basic plot
plot(mtcars$disp, mtcars$mpg)
# modify the color of the text
text(340, 30, "Sample Text", col = "red")
Description
The color of the text can be modified using the col
argument in the text() function.
Code

7. dataCrunchtext(): Color
Slide 7
The below plot depicts the appearance of the text when different options for col are applied:

8. dataCrunchtext(): Font
Slide 8
# create a basic plot
plot(mtcars$disp, mtcars$mpg)
# modify the font of the text
text(340, 30, "Sample Text", font = 2)
Description
The font of the text can be modified using the font
argument in the text() function.
Code

9. dataCrunchtext(): Font
Slide 9
The below plot depicts the appearance of the text when different options for font are applied:

10. dataCrunchtext(): Font Family
Slide 10
# create a basic plot
plot(mtcars$disp, mtcars$mpg)
# modify the font family of the text
text(340, 30, "Sample Text", family = mono)
Description
The font family of the text can be modified using the
family argument in the text() function.
Code

11. dataCrunchtext(): Font Family
Slide 11
The below plot depicts the appearance of the text when different options for font family are applied:

12. dataCrunchtext(): Font Size
Slide 12
# create a basic plot
plot(mtcars$disp, mtcars$mpg)
# modify the size of the text
text(340, 30, "Sample Text", cex = 1.5)
Description
The size of the text can be modified using the cex
argument in the text() function.
Code

13. dataCrunchtext(): Font Size
Slide 13
The below plot depicts the appearance of the text when different options for font size are applied:

14. dataCrunchmtext(): Introduction
Slide 14
The mtext() function places text annotations on the margins of the plot instead of placing them
inside the plot. It allows the user to modify the location of the text in multiple ways and we will
explore them one by one.
Below is a simple example:
# create a basic plot
plot(mtcars$disp, mtcars$mpg)
# add text
mtext("Sample Text")
As you can see, the text is placed on
the margin of the plot and not inside
the plot. Next, we will learn to
specify the margin where the text
should be placed.

15. dataCrunchmtext(): Margin
Slide 15
# create a basic plot
plot(mtcars$disp, mtcars$mpg)
# specify the margin on which the text should appear
mtext("Sample Text", side = 1)
Description
The margin on which we want to place the
text can be specified using the side
argument. It takes 4 values from 1-4 each
representing one side of the plot.
Code

16. dataCrunchmtext(): Margin Options
Slide 16
The side argument can be used to specify the margin on which the text should be placed.
side Margin
1 Bottom
2 Left
3 Top
4 Right

17. dataCrunchmtext(): Margin
Slide 17
The below plot depicts the appearance of the text when different options for side are applied:

18. dataCrunchmtext(): Line
Slide 18
# create a basic plot
plot(mtcars$disp, mtcars$mpg)
# place the text away from the margin
mtext("Sample Text", line = 1)
Description
The line argument places the text at the
specified distance from the margin. The default
value is 0 and as the value increases the text
is placed farther from the margin and outside
the plot, and as the value decreases the text is
placed inside the plot and farther from the
margin.
Code

19. dataCrunchmtext(): Line
Slide 19
# create a basic plot
plot(mtcars$disp, mtcars$mpg)
# place the text away from the plot
mtext("Sample Text", line = -1)
Description
The line argument places the text inside the
plot when the values is less than zero.
Code

20. dataCrunchmtext(): Line
Slide 20
The below plot depicts the appearance of the text when different options for line are applied:

21. dataCrunchmtext(): adj
Slide 21
# create a basic plot
plot(mtcars$disp, mtcars$mpg)
# align the text to the left
mtext("Sample Text", adj= 0)
Description
The adj argument is used for horizontal
alignment of the text. If set to 0, the text will be
left aligned and at 1, it will be right aligned.
Code

22. dataCrunchmtext(): adj
Slide 22
# create a basic plot
plot(mtcars$disp, mtcars$mpg)
# align the text to the right
mtext("Sample Text", adj= 1)
Description
When the value is set to 1, the text will be right
aligned.
Code

23. dataCrunchmtext(): adj
Slide 23
The below plot depicts the appearance of the text when different options for text() are applied:

24. dataCrunch
Slide 24
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