R Markdown is an authoring format that enables easy creation of dynamic documents, presentations, and reports from R. It combines the core syntax of markdown (an easy to write plain text format) with embedded R code chunks that are run so their output can be included in the final document. R Markdown documents are fully reproducible (they can be automatically regenerated whenever underlying R code or data changes).
With the basics described above you can get started with R Markdown right away. To learn more see:
Markdown Basics, which describes the most commonly used markdown constructs.
R Code Chunks, which goes into more depth on customizing the behavior of embedded R code.
R Markdown Cheat Sheet (PDF), a quick guide to the most commonly used markdown syntax, knitr options, and output formats.
R Markdown Reference Guide (PDF), a more comprehensive reference guide to markdown, knitr, and output format options.
Bibliographies and Citations, which describes how to include references in R Markdown documents.
Compiling Notebooks, which describes how to compile HTML, PDF, or MS Word notebooks from R scripts.
For even more in-depth documentation see:
The website for the knitr package. Knitr is an extremely powerful tool for dynamic content generation and the website has a wealth of documentation and examples to help you utilize it to its full potential.
The full specification of Pandoc Markdown, which describes all of the markdown features and syntax available within R Markdown documents.
If you are migrating documents from R Markdown v1 or wish to continue using RMarkdown v1 see the article on Migrating from R Markdown v1.
See also the R Markdown developer documentation including: