Here we'll look in more detail at chunk options in Rmarkdown which control how code and the output of the code is evaluated and displayed. A full listing of chunk options can be found at the knitr website.
(NOTE! Some students have reported getting error messages when trying to use the "Knit HTML" button on the editor toolbar. If you are having problems check the CRAN mirror setting under Tools > Global Options (Mac: RSTudio > Preferences) - it should be set to a mirror that is closer to your location.