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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
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