Re: dependence of fit with previous one

sorry,
i'm not sure to understand

i call exactly the same function for the two fits and i reinitialize the parameters and their errors
only the histogram is not the same

but i see that the digits are not exactly the same -->
how to fix the "numerical error in the function evaluation" ?

i mean the result is not reproducible if one does a previous fit : it sounds problematic, isn't it ?

 >It could be also you are using a MC integration in the function evaluation. In this case this can happen. sorry : what is a Monte-Carlo Integration ?

(i just used : myhisto->Fit("LV");

thank for any help

Lorenzo Moneta a écrit :
> Hi Marc,
>
> The fit is re-initialized correctly when you set the parameters and
> the errors. In your case, it is probably your function which returns a
> different result
> given the same parameters probably due to a numerical error in the
> function evaluation.
>
> I can see that you have a numerical problem in evaluating your
> function to minimize by seeing this error message in the log file:
> MIGRAD FAILS TO FIND IMPROVEMENT
> MACHINE ACCURACY LIMITS FURTHER IMPROVEMENT.
>
> It could be also you are using a MC integration in the function
> evaluation. In this case this can happen.
>
> Cheers,
>
> Lorenzo
> On Mar 1, 2011, at 1:08 PM, Marc Escalier wrote:
>
>> Hello,
>>
>> i observed a dependence of a given fit the previous one, *even* when
>> i reinitialize each of the parameters and their errors
>>
>> -->is there a way to "reinitialize" the fitter to have
>> reproducibility one one do some previous (or not) fits ?
>>
>> thanks a lot
>>
>> -->here is a log of the fits
>> http://users.lal.in2p3.fr/escalier/ProblemRoot/
>>
>> it begins to change here :
>> with only one fit :
>> 2 CB_mean 1.40000e+02 6.00000e-01 2.01358e-01 2.51098e+02
>>
>> with *a* previous fit before (and after having reiniatzed the
>> parameter by SetParameter and SetParError) :
>> 2 CB_mean 1.40000e+02 6.00000e-01 2.01358e-01 2.51095e+02
>>
>> at the end of the fit : it gives
>> with only one fit :
>>
>> 1 A 6.19000e+02 fixed 2 CB_mean
>> 1.39795e+02 3.64629e-02 3
>> CB_sigma 1.95380e+00 3.00964e-02
>> 4 CB_alpha 1.22909e+00
>> 4.12433e-02 5 CB_n
>> 1.00000e+01 fixed 6 Gauss_mean 1.44687e+02
>> 7.63561e-01 7 Gauss_sigma
>> 2.57589e+00 4.29212e-01 8 frac_CB
>> 9.75035e-01 5.66139e-03
>>
>> with *a* previous fit before (and after having reiniatzed the
>> parameter by SetParameter and SetParError) :
>>
>> 1 A 6.19000e+02 fixed 2 CB_mean
>> 1.39795e+02 3.72340e-02 3
>> CB_sigma 1.95381e+00 3.07984e-02
>> 4 CB_alpha 1.22910e+00
>> 4.12501e-02 5 CB_n
>> 1.00000e+01 fixed 6 Gauss_mean 1.44688e+02
>> 7.55733e-01 7 Gauss_sigma
>> 2.57555e+00 4.30838e-01 8 frac_CB
>> 9.75039e-01 5.48416e-03
>>
>> -->some digits are not exactly the same
>>
>> thanks
>>
>
Received on Tue Mar 01 2011 - 14:28:06 CET