[R] speeding up functions for large datasets

[Freja.Vamborg@astrazeneca.com]

Dear R-helpers, 
I'm dealing with large datasets, say tables of 60 000 times 12 or so, and
some of the functions are (too ) slow and I'm therefore trying to find ways
to speed them up.
I've found that for instance for-loops are slow in R (both by testing and by
searching through mail archives etc )
Are there any more well known arguments that are slow in R, ,maybe at data
representation level, code-writing, reading in the data.
I've also tried incorporating C-code, which works well, but I'd also like to
find other, maybe more "shortcut" ways.

Thanks in advance, 
Freja!