I would like to create an Rmarkdown document (pdf or html) that has some chunks "executed" conditionally.  The particular case I have in mind is that I might want a more verbose and documented vers...

The first official book authored by the core R Markdown developers that provides a comprehensive and accurate reference to the R Markdown ecosystem. With R Markdown, you can easily create reproducible data analysis reports, presentations, dashboards, interactive applications, books, dissertations, websites, and journal articles, while enjoying the simplicity of Markdown and the great power of R and other languages.