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NonlinearFit of an "implicit" function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg94321] NonlinearFit of an "implicit" function
  • From: kretch <yaronkretchmer at gmail.com>
  • Date: Wed, 10 Dec 2008 04:48:37 -0500 (EST)

Hi All
I need to perform a non linear fit of a function which is not provided
directly i.e. instead of the function having the explicit form
f(x,y,z) = ...
I have an implicit  form
1/(f(x,y,z) + x^2)^3 = ...

Now, I know I can manipulate the function so that I get an explicit
form, but since I have a variety of functions (>100), this would be
very tedious and error-prone.

So my question is this:
I'd like to get the explicit form of the function by "Solve" ing it,
then run the fit on the explicit form. But for some reason, the exact
syntax eludes me and I get error messages.

Can somebody share an example of fitting an implicit function?

Thanks
Kretch



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