NBD fit function

ROOT
1

Is it right to write NBD fit function like:

TF1 fit1 = new TF1(“fit1”,"[0](TMath::Gamma(x+[1])/(TMath::Gamma(x+1)TMath::Gamma([1])))(TMath::Power(([2]/[1]),x))*(TMath::Power((1+([2]/[1])),-x-[1]))");

? Thanks for response.

2

Your function is OK. For example you can try:

{ TF1 *fit1 = new TF1("fit1","[0]*(TMath::Gamma(x+[1])/(TMath::Gamma(x+1)*TMath::Gamma([1])))*(TMath::Power(([2]/[1]),x))*(TMath::Power((1+([2]/[1])),-x-[1]))"); fit1->SetParameters(1,.2,.2); fit1->Draw(); }
Writing a C function would probably be more efficient.

Rene