Symbolic Derivatives in R

I wrote an R package called Deriv for doing symbolic derivatives. You should follow that (official) link for the latest version, which is kindly maintained by Serguei Sokol <sokol at>. (I am keeping this unofficial page just to preserve history.) You might also find Ryacas, which is an interface to YACAS (Yet Another Computer Algebra System) that does an excellent job of differentiation, among other things.