[Rd] Is there any way to find out how a certain functions are implemented in R?

[Kyeongmi Cheon]

Hello
I wrote a bootstrap program in C language that is called and run by R.
When I tried it, it is slow

and I'm trying to write and run the whole thing in C. But I cannot use
handy functions in R and

need to figure out how to write those functions by myself. Is there
any way that I can get the

actual codes that implement functions in R so that I can translate
them into other languages? For

example, after I generate bootstrap samples in C, I want to simplify
the new dataset just like I

did it in R using "aggregate(data$variable1,
list(data$variable2,data$variable3), length) or

aggregate(data$variable1, list(data$variable2,data$variable3), sum)
etc". How could I do that in C

and is there any way to find out how it is implemented in R? Thank you.
Kyeongmi
Univ. Memphis