[R] How to remove directory?

[Xiaobo Gu]

Hi,
It seems file.remove can't remove directories,  regardless whether
it's an empty one, but how to delete a directory in R

> file.remove("D:/ffdata")
[1] FALSE
Warning message:
In file.remove("D:/ffdata") :
  cannot remove file 'D:/ffdata', reason 'Permission denied'
Thanks.
Xiaobo Gu