Derivatives of InterpolatingFunctions

*To*: mathgroup at smc.vnet.net*Subject*: [mg5021] Derivatives of InterpolatingFunctions*From*: pehowland at taz.dra.hmg.gb (Paul E Howland)*Date*: Sat, 19 Oct 1996 16:40:27 -0400*Organization*: DRA Malvern*Sender*: owner-wri-mathgroup at wolfram.com

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: 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? Many thanks, Paul __________________________________________________________ Paul E Howland, MEng CEng MIEE Tel +44-1684-895767 Long Range Ground Radar Sensors Fax +44-1684-896315 DRA Malvern Malvern, Worcs, UK __________________________________________________________