how can I evaluate the derivative of a spline function in R?

Question

R can generate a spline function using splinefun() in the splines library. However, I need to evaluate this function at its first and second derivatives. Is there a way to do this?

for example

library(splines)
x <- 1:10
y <- sin(pi/x) #just an example
f_of_x <- splinefun(x,y)

How can I evaluate f'(x) for a vector of x's?

Answer 1

It is very easy to do since the ability to evaluate the function at its derivatives is built in to the function!

 f_of_x(x, deriv = 1)

Thanks R-core!

Answer 2

You may also be interested in the TkSpline function in the TeachingDemos package which will plot the spline function along with its derivatives.