Re: Problems with FindMinimum

*To*: mathgroup at smc.vnet.net*Subject*: [mg90722] Re: Problems with FindMinimum*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Mon, 21 Jul 2008 04:29:18 -0400 (EDT)

On 7/20/08 at 6:32 AM, teodorom at hotmail.com wrote: >Hi, I'm having problems with the FindMinimum. I'm currently getting >errors like this: FindMinimum::nrlnum: The function value >{0.335521+43899.8 \ [ImaginaryI],0.376043+43899.8 >\[ImaginaryI],0.424669+43899.8 \ [ImaginaryI],<<6>>,0.311208+46311.9 >\[ImaginaryI],<<27>>} is not a list of real numbers with dimensions >{37} at {x0,y0,x1,y1,hh0,hh1} = >{0.00580647,-2.13969*10^20,-9.86301*10^-6,1.23875*10^20,-30574.3,19. >6042}. I guess this happens because the function I'm trying to fit >with experimantal data, gets imaginary values for some values of the >parameters. How can I avoid this and get meaningful results ? If you truly expect a response that is better than your guess you need to provide more details such as what is the function you are trying to fit? Meanwhile, there are a variety of things you could try such as: Specifying the method for FindMinimum to use rather than accepting the result Use NMinimize with appropriate constraints instead of FindMinimum Use FindFit instead of FindMinimum =46indFit is designed to fit a function to data. As a general rule, you will get better results with Mathematica when you use things more specific to your task than the more general things.