Syntax highlighting for R is not currently supported on Stack Exchange (see here). Currently, questions tagged r are using the "default" syntax highlighting (see in the code source of any page tagged with r the snippet
<div style="display:none" id="prettify-lang">default</div>).
However R is supported by Google-code-prettify as an extension. As the r tag just passed the 50,000-questions milestone on Stack Overflow (with an additional 5,000 on Cross Validated), would it be possible to have our syntax highlighting implemented and linked to the tag?
Edit: four months later
The r tag on Stack Overflow is now close to 60,000 questions, on Cross Validated more than 6,000 questions, a couple hundreds answers on Code Golf, 40 questions on Code Review and 9 out of the 84 questions present on the brand new Data Science beta are tagged with r.