I'm using an InterpolatingFunction to model a set of data that is a function of three variables (range,height,frequency). I need to generate the partial derivatives of this InterpolatingFunction with respect to each of the variables. Unfortunately, version 2.2 of Mathematica appears unable to do this, unless the InterpolatingFunction is a function of only one variable.
My questions are: 1. Has this been fixed in v3.0 of Mathematica? 2. If not, has anyone written a package to address this shortfall?
I know I could approximate the derivative using something along the lines of (f[x+dx,y,z]-f[x-dx,y,z])/(2dx), but I suspect that this could lead to problems if I make the wrong choice of dx. Does anyone care to comment?