Re: FindFit with conditionals

*To*: mathgroup at smc.vnet.net*Subject*: [mg57355] Re: [mg57307] FindFit with conditionals*From*: Edward Peschko <esp5 at pge.com>*Date*: Wed, 25 May 2005 06:03:05 -0400 (EDT)*References*: <200505240912.FAA19168@smc.vnet.net> <B8AB71D2-44E9-434B-BB5D-BACFA4B5579C@akikoz.net>*Sender*: owner-wri-mathgroup at wolfram.com

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 ] where <built-in-function> is a mathematica function, f[x_,y_,z_...] is an expression or series of chained expressions, and {x,y,z} is a list of arguments to pass to function, and which vary from evaluation to evaluation via global optimization tools, and Integers 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. Ed

**References**:**FindFit with conditionals***From:*Edward Peschko <esp5@pge.com>