You can format your post/comment using Markdown Reddit now has their own guide for New Reddit compatibility. Note that the styling formats are stackable with each other - you can have a link in italics, a link in a superscript, a bold strikethrough, etc. So, we created a guide to Reddit-flavored Markdown, which explains generally how to format content on new Reddit, and specifically identifies areas where new Reddit-flavored Markdown is different from old Reddit-flavored markdown. You can find the guide on our wiki.

1. Reddit Markdown Guide
2. Reddit Markdown Guide Examples

Interactive documents are a new way to build Shiny apps. An interactive document is an R Markdown file that contains Shiny widgets and outputs. You write the report in markdown, and then launch it as an app with the click of a button.

This article will show you how to write an R Markdown report.

The companion article, Introduction to interactive documents, will show you how to turn an R Markdown report into an interactive document with Shiny components.

R Markdown

R Markdown is a file format for making dynamic documents with R. An R Markdown document is written in markdown (an easy-to-write plain text format) and contains chunks of embedded R code, like the document below.

R Markdown files are designed to be used with the rmarkdown package. rmarkdown comes installed with the RStudio IDE, but you can acquire your own copy of rmarkdown from CRAN with the command

R Markdown files are the source code for rich, reproducible documents. You can transform an R Markdown file in two ways.

1. knit - You can knit the file. The rmarkdown package will call the knitr package. knitr will run each chunk of R code in the document and append the results of the code to the document next to the code chunk. This workflow saves time and facilitates reproducible reports.

   Consider how authors typically include graphs (or tables, or numbers) in a report. The author makes the graph, saves it as a file, and then copy and pastes it into the final report. This process relies on manual labor. If the data changes, the author must repeat the entire process to update the graph.

   In the R Markdown paradigm, each report contains the code it needs to make its own graphs, tables, numbers, etc. The author can automatically update the report by re-knitting.

2. convert - You can convert the file. The rmarkdown package will use the pandoc program to transform the file into a new format. For example, you can convert your .Rmd file into an HTML, PDF, or Microsoft Word file. You can even turn the file into an HTML5 or PDF slideshow. rmarkdown will preserve the text, code results, and formatting contained in your original .Rmd file.

   Conversion lets you do your original work in markdown, which is very easy to use. You can include R code to knit, and you can share your document in a variety of formats.

In practice, authors almost always knit and convert their documents at the same time. In this article, I will use the term render to refer to the two step process of knitting and converting an R Markdown file.

You can manually render an R Markdown file with rmarkdown::render(). This is what the above document looks like when rendered as a HTML file.

In practice, you do not need to call rmarkdown::render(). You can use a button in the RStudio IDE to render your reprt. R Markdown is heavily integrated into the RStudio IDE.

Getting started

To create an R Markdown report, open a plain text file and save it with the extension .Rmd. You can open a plain text file in your scripts editor by clicking File > New File > Text File in the RStudio toolbar.

Be sure to save the file with the extension .Rmd. The RStudio IDE enables several helpful buttons when you save the file with the .Rmd extension. You can save your file by clicking File > Save in the RStudio toolbar.

R Markdown reports rely on three frameworks

1. markdown for formatted text
2. knitr for embedded R code
3. YAML for render parameters

The sections below describe each framework.

Markdown for formatted text

.Rmd files are meant to contain text written in markdown. Markdown is a set of conventions for formatting plain text. You can use markdown to indicate

• bold and italic text
• lists
• headers (e.g., section titles)
• hyperlinks
• and much more

The conventions of markdown are very unobtrusive, which make Markdown files easy to read. The file below uses several of the most useful markdown conventions.

The file demonstrates how to use markdown to indicate:

1. headers - Place one or more hashtags at the start of a line that will be a header (or sub-header). For example, # Say Hello to markdown. A single hashtag creates a first level header. Two hashtags, ##, creates a second level header, and so on.

2. italicized and bold text - Surround italicized text with asterisks, like this *without realizing it*. Surround bold text with two asterisks, like this **easy to use**.

3. lists - Group lines into bullet points that begin with asterisks. Leave a blank line before the first bullet, like this

4. hyperlinks - Surround links with brackets, and then provide the link target in parentheses, like this [Github](www.github.com).

You can learn about more of markdown’s conventions in the Markdown Quick Reference guide, which comes with the RStudio IDE.

To access the guide, open a .md or .Rmd file in RStudio. Then click the question mark that appears at the top of the scripts pane. Next, select “Markdown Quick Reference”. RStudio will open the Markdown Quick Reference guide in the Help pane.

Rendering

To transform your markdown file into an HTML, PDF, or Word document, click the “Knit” icon that appears above your file in the scripts editor. A drop down menu will let you select the type of output that you want.

When you click the button, rmarkdown will duplicate your text in the new file format. rmarkdown will use the formatting instructions that you provided with markdown syntax.

Once the file is rendered, RStudio will show you a preview of the new output and save the output file in your working directory.

Here is how the markdown script above would look in each output format.

Note: RStudio does not build PDF and Word documents from scratch. You will need to have a distribution of Latex installed on your computer to make PDFs and Microsoft Word (or a similar program) installed to make Word files.

knitr for embedded R code

The knitr package extends the basic markdown syntax to include chunks of executable R code.

When you render the report, knitr will run the code and add the results to the output file. You can have the output display just the code, just the results, or both.

To embed a chunk of R code into your report, surround the code with two lines that each contain three backticks. After the first set of backticks, include {r}, which alerts knitr that you have included a chunk of R code. The result will look like this

When you render your document, knitr will run the code and append the results to the code chunk. knitr will provide formatting and syntax highlighting to both the code and its results (where appropriate).

As a result, the markdown snippet above will look like this when rendered (to HTML).

To omit the results from your final report (and not run the code) add the argument eval = FALSE inside the brackets and after r. This will place a copy of your code into the report.

To omit the code from the final report (while including the results) add the argument echo = FALSE. This will place a copy of the results into your report.

echo = FALSE is very handy for adding plots to a report, since you usually do not want to see the code that generates the plot.

echo and eval are not the only arguments that you can use to customize code chunks. You can learn more about formatting the output of code chunks at the rmarkdown and knitr websites.

Inline code

To embed R code in a line of text, surround the code with a pair of backticks and the letter r, like this.

knitr will replace the inline code with its result in your final document (inline code is always replaced by its result). The result will appear as if it were part of the original text. For example, the snippet above will appear like this:

YAML for render parameters

You can use a YAML header to control how rmarkdown renders your .Rmd file. A YAML header is a section of key: value pairs surrounded by --- marks, like below

The output: value determines what type of output to convert the file into when you call rmarkdown::render(). Note: you do not need to specify output: if you render your file with the RStudio IDE knit button.

output: recognizes the following values:

• html_document, which will create HTML output (default)
• pdf_document, which will create PDF output
• word_document, which will create Word output

If you use the RStudio IDE knit button to render your file, the selection you make in the gui will override the output: setting.

Slideshows

You can also use the output: value to render your document as a slideshow.

• output: ioslides_presentation will create an ioslides (HTML5) slideshow
• output: beamer_presentation will create a beamer (PDF) slideshow

Note: The knit button in the RStudio IDE will update to show slideshow options when you include one of the above output values and save your .Rmd file.

rmarkdown will convert your document into a slideshow by starting a new slide at each header or horizontal rule (e.g., ***).

Visit rmakdown.rstudio.com to learn about more YAML options that control the render process.

Recap

R Markdown documents provide quick, reproducible reporting from R. You write your document in markdown and embed executable R code chunks with the knitr syntax.

You can update your document at any time by re-knitting the code chunks.

You can then convert your document into several common formats.

R Markdown documents implement Donald’s Knuth’s idea of literate programming and take the manual labor out of writing and maintaining reports. Moreover, they are quick to learn. You already know ecnough about markdown, knitr, and YAML to begin writing your own R Markdown reports.

In the next article, Introduction to interactive documents, you will learn how to add interactive Shiny components to an R Markdown report. This creates a quick workflow for writing light-weight Shiny apps.

To learn more about R Markdown and interactive documents, please visit rmarkdown.rstudio.com.

What is Markdown?

Markdown is a lightweight markup language that you can use to add formatting elements to plaintext text documents. Created by John Gruber in 2004, Markdown is now one of the world’s most popular markup languages.

Using Markdown is different than using a WYSIWYG editor. In an application like Microsoft Word, you click buttons to format words and phrases, and the changes are visible immediately. Markdown isn’t like that. When you create a Markdown-formatted file, you add Markdown syntax to the text to indicate which words and phrases should look different.

For instance, to denote a heading, you add a number sign before it (e.g., # Heading One). Or to make a phrase bold, you add two asterisks before and after it (e.g., **this text is bold**). It may take a while to get used to seeing Markdown syntax in your text, especially if you’re accustomed to WYSIWYG applications. The screenshot below shows a Markdown file displayed in the Atom text editor.

You can add Markdown formatting elements to a plaintext file using a text editor application. Or you can use one of the many Markdown applications for macOS, Windows, Linux, iOS, and Android operating systems. There are also several web-based applications specifically designed for writing in Markdown.

Depending on the application you use, you may not be able to preview the formatted document in real time. But that’s okay. According to Gruber, Markdown syntax is designed to be readable and unobtrusive, so the text in Markdown files can be read even if it isn’t rendered.

The overriding design goal for Markdown’s formatting syntax is to make it as readable as possible. The idea is that a Markdown-formatted document should be publishable as-is, as plain text, without looking like it’s been marked up with tags or formatting instructions.

Why Use Markdown?

You might be wondering why people use Markdown instead of a WYSIWYG editor. Why write with Markdown when you can press buttons in an interface to format your text? As it turns out, there are a couple different reasons why people use Markdown instead of WYSIWYG editors.

• Markdown can be used for everything. People use it to create websites, documents, notes, books, presentations, email messages, and technical documentation.

• Markdown is portable. Files containing Markdown-formatted text can be opened using virtually any application. If you decide you don’t like the Markdown application you’re currently using, you can import your Markdown files into another Markdown application. That’s in stark contrast to word processing applications like Microsoft Word that lock your content into a proprietary file format.

• Markdown is platform independent. You can create Markdown-formatted text on any device running any operating system.

• Markdown is future proof. Even if the application you’re using stops working at some point in the future, you’ll still be able to read your Markdown-formatted text using a text editing application. This is an important consideration when it comes to books, university theses, and other milestone documents that need to be preserved indefinitely.

• Markdown is everywhere. Websites like Reddit and GitHub support Markdown, and lots of desktop and web-based applications support it.

Kicking the Tires

The best way to get started with Markdown is to use it. That’s easier than ever before thanks to a variety of free tools.

You don’t even need to download anything. There are several online Markdown editors that you can use to try writing in Markdown. Dillinger is one of the best online Markdown editors. Just open the site and start typing in the left pane. A preview of the rendered document appears in the right pane.

You’ll probably want to keep the Dillinger website open as you read through this guide. That way you can try the syntax as you learn about it. After you’ve become familiar with Markdown, you may want to use a Markdown application that can be installed on your desktop computer or mobile device.

How Does it Work?

Dillinger makes writing in Markdown easy because it hides the stuff happening behind the scenes, but it’s worth exploring how the process works in general.

When you write in Markdown, the text is stored in a plaintext file that has an .md or .markdown extension. But then what? How is your Markdown-formatted file converted into HTML or a print-ready document?

The short answer is that you need a Markdown application capable of processing the Markdown file. There are lots of applications available — everything from simple scripts to desktop applications that look like Microsoft Word. Despite their visual differences, all of the applications do the same thing. Like Dillinger, they all convert Markdown-formatted text to HTML so it can be displayed in web browsers.

Markdown applications use something called a Markdown processor (also commonly referred to as a “parser” or an “implementation”) to take the Markdown-formatted text and output it to HTML format. At that point, your document can be viewed in a web browser or combined with a style sheet and printed. You can see a visual representation of this process below.

To summarize, this is a four-part process:

1. Create a Markdown file using a text editor or a dedicated Markdown application. The file should have an .md or .markdown extension.
2. Open the Markdown file in a Markdown application.
3. Use the Markdown application to convert the Markdown file to an HTML document.
4. View the HTML file in a web browser or use the Markdown application to convert it to another file format, like PDF.

From your perspective, the process will vary somewhat depending on the application you use. For example, Dillinger essentially combines steps 1-3 into a single, seamless interface — all you have to do is type in the left pane and the rendered output magically appears in the right pane. But if you use other tools, like a text editor with a static website generator, you’ll find that the process is much more visible.

What’s Markdown Good For?

Markdown is a fast and easy way to take notes, create content for a website, and produce print-ready documents.

It doesn’t take long to learn the Markdown syntax, and once you know how to use it, you can write using Markdown just about everywhere. Most people use Markdown to create content for the web, but Markdown is good for formatting everything from email messages to grocery lists.

Here are some examples of what you can do with Markdown.

Websites

Markdown was designed for the web, so it should come as no surprise that there are plenty of applications specifically designed for creating website content.

If you’re looking for the simplest possible way to create a website with Markdown files, check out blot.im and smallvictori.es. After you sign up for one of these services, they create a Dropbox folder on your computer. Just drag and drop your Markdown files into the folder and — poof! — they’re on your website. It couldn’t be easier.

If you’re familiar with HTML, CSS, and version control, check out Jekyll, a popular static site generator that takes Markdown files and builds an HTML website. One advantage to this approach is that GitHub Pages provides free hosting for Jekyll-generated websites. If Jekyll isn’t your cup of tea, just pick one of the many other static site generators available.

If you’d like to use a content management system (CMS) to power your website, take a look at Ghost. It’s a free and open-source blogging platform with a nice Markdown editor. If you’re a WordPress user, you’ll be happy to know there’s Markdown support for websites hosted on WordPress.com. Self-hosted WordPress sites can use the Jetpack plugin.

Documents

Markdown doesn’t have all the bells and whistles of word processors like Microsoft Word, but it’s good enough for creating basic documents like assignments and letters. You can use a Markdown document authoring application to create and export Markdown-formatted documents to PDF or HTML file format. The PDF part is key, because once you have a PDF document, you can do anything with it — print it, email it, or upload it to a website.

Here are some Markdown document authoring applications I recommend:

• Mac:MacDown, iA Writer, or Marked
• iOS / Android:iA Writer
• Windows:ghostwriter or Markdown Monster
• Linux:ReText or ghostwriter
• Web:Dillinger or StackEdit

Notes

In nearly every way, Markdown is the ideal syntax for taking notes. Sadly, Evernote and OneNote, two of the most popular note applications, don’t currently support Markdown. The good news is that several other note applications do support Markdown:

• Simplenote is a free, barebones note-taking application available for every platform.
• Notable is a note-taking application that runs on a variety of platforms.
• Bear is an Evernote-like application available for Mac and iOS devices. It doesn’t exclusively use Markdown by default, but you can enable Markdown compatibility mode.
• Boostnote bills itself as an “open source note-taking app designed for programmers.”

If you can’t part with Evernote, check out Marxico, a subscription-based Markdown editor for Evernote, or use Markdown Here with the Evernote website.

Books

Looking to self-publish a novel? Try Leanpub, a service that takes your Markdown-formatted files and turns them into an electronic book. Leanpub outputs your book in PDF, EPUB, and MOBI file format. If you’d like to create paperback copies of your book, you can upload the PDF file to another service such as Kindle Direct Publishing. To learn more about writing and self-publishing a book using Markdown, read this blog post.

Presentations

Believe it or not, you can generate presentations from Markdown-formatted files. Creating presentations in Markdown takes a little getting used to, but once you get the hang of it, it’s a lot faster and easier than using an application like PowerPoint or Keynote. Remark (GitHub project) is a popular browser-based Markdown slideshow tool, as is Cleaver (GitHub project). If you use a Mac and would prefer to use an application, check out Deckset or Marked.

Email

If you send a lot of email and you’re tired of the formatting controls available on most email provider websites, you’ll be happy to learn there’s an easy way to write email messages using Markdown. Markdown Here is a free and open-source browser extension that converts Markdown-formatted text into HTML that’s ready to send.

Collaboration

Collaboration and team messaging applications are a popular way of communicating with coworkers and friends at work and home. These applications don’t utilize all of Markdown’s features, but the features they do provide are fairly useful. For example, the ability to bold and italicize text without using the WYSIWYG interface is pretty handy. Slack, Discord, and Mattermost are all good collaboration applications.

Documentation

Markdown is a natural fit for technical documentation. Companies like GitHub are increasingly switching to Markdown for their documentation — check out their blog post about how they migrated their Markdown-formatted documentation to Jekyll. If you write documentation for a product or service, take a look at these handy tools:

• Read the Docs can generate a documentation website from your open source Markdown files. Just connect your GitHub repository to their service and push — Read the Docs does the rest. They also have a service for commercial entities.
• MkDocs is a fast and simple static site generator that’s geared towards building project documentation. Documentation source files are written in Markdown and configured with a single YAML configuration file. MkDocs has several built in themes, including a port of the Read the Docs documentation theme for use with MkDocs. One of the newest themes is MkDocs Material.
• Docusaurus is a static site generator designed exclusively for creating documentation websites. It supports translations, search, and versioning.
• VuePress is a static site generator powered by Vue and optimized for writing technical documentation.
• Jekyll was mentioned earlier in the section on websites, but it’s also a good option for generating a documentation website from Markdown files. If you go this route, be sure to check out the Jekyll documentation theme.

Flavors of Markdown

One of the most confusing aspects of using Markdown is that practically every Markdown application implements a slightly different version of Markdown. These variants of Markdown are commonly referred to as flavors. It’s your job to master whatever flavor of Markdown your application has implemented.

To wrap your head around the concept of Markdown flavors, it might help to think of them as language dialects. People in Ciudad Juárez speak Spanish just like the people in Barcelona, but there are substantial differences between the dialects used in both cities. The same is true for people using different Markdown applications. Using Dillinger to write with Markdown is a vastly different experience than using Ulysses.

Practically speaking, this means you never know exactly what a company means when they say they support “Markdown.” Are they talking about only the basic syntax elements, or all of the basic and extended syntax elements combined, or some arbitrary combination of syntax elements? You won’t know until you read the documentation or start using the application.

If you’re just starting out, the best advice I can give you is to pick a Markdown application with good Markdown support. That’ll go a long way towards maintaining the portability of your Markdown files. You might want to store and use your Markdown files in other applications, and to do that you need to start with an application that provides good support. You can use the tool directory to find an application that fits the bill.

Additional Resources

Reddit Markdown Guide

There are lots of resources you can use to learn Markdown. Here are some other introductory resources:

• John Gruber’s Markdown documentation. The original guide written by the creator of Markdown.
• Markdown Tutorial. An open source website that allows you to try Markdown in your web browser.
• Awesome Markdown. A list of Markdown tools and learning resources.
• Typesetting Markdown. A multi-part series that describes an ecosystem for typesetting Markdown documents using pandoc and ConTeXt.

Take your Markdown skills to the next level.

Reddit Markdown Guide Examples

Learn Markdown in 60 pages. Designed for both novices and experts, The Markdown Guide book is a comprehensive reference that has everything you need to get started and master Markdown syntax.

Want to learn more Markdown?

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