Nonlinear curve-fitting difficult functions
- To: mathgroup at smc.vnet.net
- Subject: [mg6579] Nonlinear curve-fitting difficult functions
- From: Jeff Hammock <hammockj at email.uah.edu>
- Date: Fri, 4 Apr 1997 02:11:31 -0500 (EST)
- Organization: The University of Alabama in Huntsville
- Sender: owner-wri-mathgroup at wolfram.com
Hi, I frequently use the MMA package Statistics`NonlinearFit` to perform fits to data using equations such as: f[x_,y_,]:= x Sin[y] The package uses the Levenberg-Marquardt method to itteratively find the best-fit solution. This works fine if I have a nice closed-form solution with well-behaved derivatives. I WANT to be able to use model functions like: f[x_,y_]:= NIntegrate[g[x,i],{i,0,y}] or ANY other function that I can generate that does not have a closed-form solution. Does anyone know a trick to force the existing MMA package into using numerically calculated derivatives in its optimization? Or, has anyone written a nonlinear fitting routine that handles this type of functions? Thanks in advance for any insights.... Matt *************************************** Matthew Smith, Ph.D. Research Scientist The University of Alabama in Huntsville smithmh at email.uah.edu ***************************************