I\'ve worked in the past a good deal with knitr and beamer for slides. One thing I\'m noticing now with R Presentations that dynamic sizing of both the code box and the size
@Florian's answer didn't work for me. I found a solution here that seems cleaner - credit to Andy Lyons for this fix.
Define a new style for smaller code at the beginning of the document, then apply it whenever you want the slide to use smaller code.
Here's an example of how to do it:
Presentation Title
========================================================
author: Jane Doe
transition: none
Slide 1 - large code
========================================================
Regular slide text here
```{r}
head(cars)
```
Slide 2 - small code
========================================================
class: small-code
More regular slide text...
```{r}
head(cars)
```