Re: how to create a fit inside my own class?

Dear Lorenzo

        Thank you! That is a great example. (I almost had it right, I only had to change my ROOT::Math::Functor call following your example, and then my class worked as desired.)

	yours,
		Steve

On May 17, 2011, at 10:21 AM, Lorenzo Moneta wrote:

> Hi Steve,
>
> If you want to use a member function of a class for defining your objective function (i.e. the chi2 function), you can do it by using the ROOT::Math::Minimizer and ROOT::Math::Functor class.
> If you want to use the interpreter you need to call a special constructor of the ROOT::Math::Functor class.
> I attach below a modified version of the tutorial, NumericalMinimization.C, which works for a class member function
>
> Best Regards
>
> Lorenzo
>
> <NumericalMinimization.C>
>
> On May 16, 2011, at 9:09 PM, Stephen Pate wrote:
>

>> Dear Rooters
>> 
>> 	I want to create a class, with the following characteristics:
>> 
>> (1) reads in private data at the time the class object is instantiated
>> (2) has a member function that will calculate a chi-squared comparing that data to a model
>> (3) has another member function that will perform a fit using the member chi-squared function, calling on minuit/migrad to do so
>> 
>> I would like to use the interpreter, not compiled code, at least in the beginning while I am developing my process.
>> 
>> (1) and (2) are standard things to do, but in trying to do (3) I run into the problem that the address of the member chi-squared function cannot be passed to the "SetFCN" or "SetFunction" call because it "is not defined in current scope".  I can call from one member function to another, no problem, but I can't pass the address of the member chi-squared function to the fitter interface.
>> 
>> 	All of the code works as long as I don't try to wrap it all into a class; it is only when placed inside a class that the call to "SetFCN" or "SetFunction" does not work.
>> 
>> 	There are many fitting interfaces in ROOT.  I have tried to do this using TVirtualFitter; I also tried a combination of ROOT::Math::Minimizer, ROOT::Math::Factory, and ROOT::Math::Functor; both methods were successful until placed inside a class.  It occurs to me that I have simply not tried the right interface yet, or that I need to do something additional to be able to get the address of the member function.  I hope someone can help me to do this.
>> 
>> 	I am using ROOT 5.28/00c on a MacBook Pro 10.6.7, i.e. everything is up-to-date.
>> 
>> 	thanks,
>> 		Steve Pate
>> 

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Stephen Pate            Department of Physics           office:   575-646-2135
                        New Mexico State University     dept:     575-646-3831
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skype: sfpate                                           skype:    575-680-1261