I wrote a very simple class to fit a histogram with a superposition of two other histograms. The fit is performed defining a TF1 function whose parameters are simply the integrals of the two histograms used for the sum. The TF1 function is defined using a Double_t method defined within the class itself. I attach the .cxx and .h of the class (I retained the essential parts only) to illustrate the problem: when I try to compile the class within ROOT, the compiler complains because it apparently cannot recognize the method I used to define the TF1:
no matching function for call to ‘TF1::TF1(const char [12], , Double_t&, Double_t&, int)
The problem disappears if I declare the Double_t method as static, but then the compiler complains because I cannot use the TH1F members of the class inside the Double_t method.
Hi,
you should create a TF1 as shown in the documentation of the class for last case (TF1 from a member function of a class): root.cern.ch/root/htmldoc/TF1.html#F5
a function created in this way can be used as a fit function? May I set its parameters in the usual way and use the Fit(…) methods of TH1D and TGraph without exceptional cares?
Thanks,
Antonio
[quote=“moneta”]Hi,
you should create a TF1 as shown in the documentation of the class for last case (TF1 from a member function of a class): root.cern.ch/root/htmldoc/TF1.html#F5
Yes. it is a TF1 object and can be used in all the methods which takes it as input.
The only limitation is the same one as for free C functions, it cannot be stored in a file, since it requires some code. So, when you write in a file (or when you use TF1::Clone) the function will be sampled in Npx points and only these values will be saved
Hi Lorenzo,
thank you for clarifying the point. The machinery now works fine
Antonio
[quote=“moneta”]Yes. it is a TF1 object and can be used in all the methods which takes it as input.
The only limitation is the same one as for free C functions, it cannot be stored in a file, since it requires some code. So, when you write in a file (or when you use TF1::Clone) the function will be sampled in Npx points and only these values will be saved
