[R] Calculate mean slope of a function

Hallo, hope you can help me with this question: I have calculated a function using f<-smooth.spline(data) and approxfun(f). Now I want to calculate the mean slope of the resulting function. Haven't found the right R command yet, maybe you can give me a hint. Thanx, Antje ___

[R] Changing style for groups in xyplot

Hello, I have a (hopefully) quick question concerning the xyplot function. The xyplot works very fine for me - I am using it to display functions of two variates depending on several other factors. I am therefor also using the groups argument, so that the symbols in each panel appear in different