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Re: FindFit with conditionals

  • To: mathgroup at
  • Subject: [mg57355] Re: [mg57307] FindFit with conditionals
  • From: Edward Peschko <esp5 at>
  • Date: Wed, 25 May 2005 06:03:05 -0400 (EDT)
  • References: <> <>
  • Sender: owner-wri-mathgroup at

On Tue, May 24, 2005 at 09:24:38PM +0900, Andrzej Kozlowski wrote:
> First , FindInstance does not hold its arguments (look at Attributes 
> [FindInstance]) so of course it tries to evaluate NIntegrate[...] and  
> you get he message complaining that the integrand is not numerical.
> Secondly, FindInstance uses similar methods to Reduce, which means it  
> is esentially an "algebraic" function which uses exact methods. You  
> can use it with non-exact inputs but I believe it will still use  
> exact methods to find the answer, and it will not, I think,   
> internaly perform any non-exact computations of the kind that you are  
> trying to use. (Of course it will evaluate "non-exact" functions  
> suplied as argumetns and it may use some "exact numerical methods"  
> but still the main point is, I think, valid, and that it that like  
> Reduce, it attempts to give exact answers and is not suitable for  
> solving numerical (approximate) questions.

Fair enough - 

but that still leaves me with the question - what's the best way to do this then?

IMO there should be (IMO) an easy way to say:

	<built-in-function> [ f[x_,y_,z_], {x,y,z}, Integers ]


is a mathematica function, 


is an expression or series of chained expressions, and 


is a list of arguments to pass to function, and which vary from evaluation 
to evaluation via global optimization tools, and


which is the domain over which {x,y,z} can vary.

I'm agnostic on the algorithm being deterministic, algebraic, or approximative,
but IMO this would be a very expressive way of solving problems that otherwise
would be very messy.

Just my 2 cents.


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