1.5 Text Formatting in R Markdown

You’ve learned about the powerful YAML header and the utility of R Code Chunks in Section 1.4. Now, your journey continues into the art of text formatting. A well-formatted report is not just professional; it’s a powerful tool to guide your reader through your data story.

R Markdown uses Pandoc’s Markdown, a simple yet powerful syntax for creating beautifully formatted documents. Think of the text in your .Rmd file as your raw materials (marked-up text), and the knitted document as your polished creation (formatted text).

Let’s explore the tools at your disposal.

1.5.1 Headers: Your Document’s Signposts

Use different numbers of hash symbols (#) to create up to six levels of headers. More # symbols mean a lower-level header.

# Level 1: The Chapter Title
## Level 2: A Major Section
### Level 3: A Subsection
#### Level 4: A Sub-subsection
##### Level 5: A Sub-sub-subsection
###### Level 6: A Sub-sub-sub-subsection

Pro-Tip: Set number_sections: true in the YAML header to automatically number your sections.

1.5.2 Emphasis: Making Your Point

Markdown allows you to emphasize text in various ways. Here are some common styles:

Style	Syntax	Example
Italics	`text` or `_text_`	For emphasis or scientific names
Bold	`text` or `__text__`	To show strong importance
~~Strikethrough~~	`~~text~~`	~~This idea was later disproven.~~
`Code Font`	`text`	Use for `function_names()` or `variables`.

1.5.3 Inline Code: Displaying and Evaluating

You can include code within your sentences in two ways:

To display code as text: Wrap it in single backticks. For example, 1 + 1 renders as 1 + 1.
To evaluate code and show its output: Use inline R code with `r `. For example, `r 1 + 1` evaluates to 2 in the output.

Heads‑up: Never wrap code inside a code chunk with back‑ticks: knitr() will treat them as unmatched delimiters and throw an error when you knit.

Figure 1.33: Incorrect back-ticks in a code chunck

Figure 1.34: The error message

1.5.4 Lists: Ordered and Unordered

Use lists to organize information and break down complex topics.

Unordered Lists: Start each line with *, +, or -.
Ordered Lists: Start each line with a number. R Markdown will automatically sequence them correctly, even if you use 1. for every item.
Nested Lists: Indent items to create sub-lists. You can mix and match ordered and unordered lists.

Here is an example of a mixed list:

1.  First, collect the data.
2.  Second, clean the data.
    * Check for missing values (`NA`).
    * Ensure correct data types.
3.  Finally, analyze the data.

First, collect the data.
Second, clean the data.
- Check for missing values (NA).
- Ensure correct data types.
Finally, analyze the data.

1.5.5 Hyperlinks: Connecting to the World

Guide your readers to external resources with hyperlinks. The format is [Text to display](URL).

I have learned R from the book [r02pro](https://r02pro.github.io/).

This will create a clickable link in the output document that says

I have learned R from the book r02pro.

1.5.6 Blockquotes: Highlighting Wisdom

Use the > character to create a blockquote. This is perfect for quoting sources or emphasizing a key insight.

> "The best thing about being a statistician is that you get to play in everyone's backyard." - John Tukey

This will generate

“The best thing about being a statistician is that you get to play in everyone’s backyard.” - John Tukey

1.5.7 Footnotes: Adding Extra Details

Add non-essential details or citations using footnotes. Use [^1] for the marker and define it anywhere in your document. A more convenient inline method is ^[Your footnote text here.].

This is a statement with a footnote.[^1]

[^1]: This is the footnote text that provides additional information.

This is a statement with a footnote.¹

1.5.8 The Language of the Universe: Writing Mathematics

R Markdown allows you to write beautiful mathematics using LaTeX syntax.

1.5.8.1 Inline Equations

For small formulas that fit within a line of text, wrap your LaTeX code in single dollar signs ($).

**Fun Fact:** Did you know that Euler's Identity, 
$e^{i\pi} + 1 = 0$, connects five of the most fundamental constants in mathematics?

Fun Fact: Did you know that Euler’s Identity, $e^{i\pi} + 1 = 0$, connects five of the most fundamental constants in mathematics?

1.5.8.2 Displayed Equations

For larger equations that deserve their own line, wrap them in double dollar signs ($$).

*Statistical Insight:* The probability density function of the normal distribution $N(\mu, \sigma^2)$, a cornerstone of statistics, is given by:
$$ f(x) = \frac{1}{\sqrt{2\pi\sigma^2}} e^{-\frac{(x-\mu)^2}{2\sigma^2}} $$

Statistical Insight: The probability density function of the normal distribution $N(\mu, \sigma^2)$, a cornerstone of statistics, is given by: \[ f(x) = \frac{1}{\sqrt{2\pi\sigma^2}} e^{-\frac{(x-\mu)^2}{2\sigma^2}} \]

1.5.9 Tables: From Simple to Stunning

You can create simple tables using Markdown syntax. For example:

| Operator | Description    |
|----------|----------------|
| `+`      | Addition       |
| `-`      | Subtraction    |
| `*`      | Multiplication |
| `/`      | Division       |

Operator	Description
`+`	Addition
`-`	Subtraction
`*`	Multiplication
`/`	Division

In later chapters, you will learn how to automatically generate tables from your data using R functions.

1.5.10 Your Turn: A Mini-Challenge

Time to get your hands dirty! Create a new .Rmd file and try to build the following mini-report. This is the best way to solidify your new skills.

Create a Level 1 Header: “My Favorite Mathematical Constant”
Write a sentence in bold explaining what your favorite constant is (e.g., My favorite constant is $\pi$).
Add a blockquote with a fun fact about it.
Create an ordered list with at least two reasons why you like it.
Include an inline R calculation. For example: “A circle with a radius of 5 units has a circumference of `r 2 * pi * 5` units.”
Add a footnote with a link to a Wikipedia article about your chosen constant.

Good luck, and happy formatting!

An example .Rmd file is below for your reference.

---
title: "Mini-Challenge Solution: My Favorite Mathematical Constant"
output: html_document
---

# My Favorite Mathematical Constant

**My favorite constant is  $e$**

> Euler's number, $e$, is approximately 2.71828 and is the base of the natural logarithm. It appears everywhere in growth processes, probability, and calculus!

Here are a few reasons why I like $e$:

1. It describes continuous growth and exponential change perfectly.
2. It has deep connections to calculus, particularly in limits and derivatives.

For example, if something grows continuously at a rate of 100%, after 1 unit of time it grows to:

`r exp(1)` units.

You can learn more about $e$ on its [Wikipedia page](https://en.wikipedia.org/wiki/E_(mathematical_constant)).[^1]

[^1]: Wikipedia article: https://en.wikipedia.org/wiki/E_(mathematical_constant)

This is the footnote text that provides additional information.↩︎