# Chapter 20 Introduction

Hooray! Yoohoo! Oh boy! You can label chapter and section titles using {#label} after them, e.g., we can reference Chapter 20. If you do not manually label them, there will be automatic labels anyway, e.g., Chapter 22.

Figures and tables with captions will be placed in figure and table environments, respectively.

par(mar = c(4, 4, .1, .1))
plot(pressure, type = 'b', pch = 19)

Reference a figure by its code chunk label with the fig: prefix, e.g., see Figure 20.1. Similarly, you can reference tables generated from knitr::kable(), e.g., see Table 20.1.

knitr::kable(
head(iris, 20), caption = 'Here is a nice table!',
booktabs = TRUE
)
Table 20.1: Here is a nice table!
Sepal.Length Sepal.Width Petal.Length Petal.Width Species
5.1 3.5 1.4 0.2 setosa
4.9 3.0 1.4 0.2 setosa
4.7 3.2 1.3 0.2 setosa
4.6 3.1 1.5 0.2 setosa
5.0 3.6 1.4 0.2 setosa
5.4 3.9 1.7 0.4 setosa
4.6 3.4 1.4 0.3 setosa
5.0 3.4 1.5 0.2 setosa
4.4 2.9 1.4 0.2 setosa
4.9 3.1 1.5 0.1 setosa
5.4 3.7 1.5 0.2 setosa
4.8 3.4 1.6 0.2 setosa
4.8 3.0 1.4 0.1 setosa
4.3 3.0 1.1 0.1 setosa
5.8 4.0 1.2 0.2 setosa
5.7 4.4 1.5 0.4 setosa
5.4 3.9 1.3 0.4 setosa
5.1 3.5 1.4 0.3 setosa
5.7 3.8 1.7 0.3 setosa
5.1 3.8 1.5 0.3 setosa

You can write citations, too. For example, we are using the bookdown package (Xie 2018) in this sample book, which was built on top of R Markdown and knitr (Xie 2015).

### References

Xie, Yihui. 2018. Bookdown: Authoring Books and Technical Documents with R Markdown. https://github.com/rstudio/bookdown.

Xie, Yihui. 2015. Dynamic Documents with R and Knitr. 2nd ed. Boca Raton, Florida: Chapman; Hall/CRC. http://yihui.name/knitr/.