I'm reworking all of my completed Project Euler problems in R.
For the most part, I'm trying to stick with base R when possible. I will however, be shamlessly using the Hadley Wickham packages (plyr, stringr, ggmap, ggplot2, reshape2, etc) and math packages that have functions pre-built for things are necessary but would be tedious (prime finding, etc).
The key for me here is to work through the problem first in R so I get a better grasp on coding in the language rather than just dinking around with it. After that, I can go back and redo things building my own functions for stuff I used out of packages.
Thus far I have 23 solved, almost all of them some sort of number theory. That's not out of a great love of number theory so much as those seem like the ones most easily done without a graduate-level math education.
But I'll be tackling the big hairy ones too, as soon as I finish reworking these 23 in R.