I just installed the binary for root v 6.10.00 on my macOS 10.11.4.
Now code using TFractionFitter leads to the following compilation error:
error: no member named ‘FixParameter’ in ‘ROOT::Fit::Fitter’
the offending line is fit->GetFitter()->FixParameter(i);
where ‘fit’ is a TFractionFitter*.
So it seems that this function returns a Fit::Fitter object, not a TVirtualFitter as before. Is that correct? If so, how can I fix a parameters in the TFractionFitter, fix parameters and ask for the number of free parameters? I guess this can be done using the FitConfig class but I had little luck finding documentation how to use this class.