[R] Function rank() for data frames (or multiple vectors)?

[Sebastian Bauer]

Hello,

I'd like to rank rows of a data frame similar to what rank() does for 
vectors. However, ties should be broken by columns that I specify. If it 
is not possible to break a ties (because the row data is essentially the 
same), I'd like to have the same flexibility that rank() offers. Is 
there an elegant solution to this simple problem in R? Basically, what I 
need is a mixture of order() and rank(). While the former allows to 
specify multiple vectors, it doesn't provide the flexibility of rank() 
such that I can specify what happens if ties can not be broken.

Thanks for your help!

Best,
Sebastian