Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
1999
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 1999

[Date Index] [Thread Index] [Author Index]

Search the Archive

Nonlinear Fit with complex model

  • To: mathgroup at smc.vnet.net
  • Subject: [mg19605] Nonlinear Fit with complex model
  • From: mtir at my-deja.com
  • Date: Sat, 4 Sep 1999 21:09:13 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

I am trying to fit a data set of real values with
a model that involves complex numbers, i.e.
  model[a,b,c,d]=Abs[<complex expression in
a,b,c,d>]^2

When I am using NonlinearRegress (or
NonlinearFit) Mathematica complains that "One or
more derivatives of the model with respect to
parameters did not evaluate" and does not return a
result.

I suspect that the reason for this is that Abs[],
Re[], Im[] etc. are not evaluated if the argument
is an expression rather than a number.

Does anyone know a way round this?

Thanks!
Sebastian

(For those interested: I am trying to calculate
the complex refractive index of a thin film from
reflectance measurements as a function of angle)


Sent via Deja.com http://www.deja.com/
Share what you know. Learn what you don't.


  • Prev by Date: Re: axes in ListPlot
  • Next by Date: FindMinimum to minimize e . w . e
  • Previous by thread: Re: Multiple sum with iterators that cannot equal
  • Next by thread: Re: Nonlinear Fit with complex model