Parameters of ROOT::Math::legendre([0],x)

Roofit and RooStats
1

Dear all,

I need to fit a TGraph with a sum of Legendre polynomials. One way is to write polynomials by hands and another is to use ROOT::Math::legendre([0],x). I looked into a /root/tutorials/math/Legendre.C to learn how it works and I have a question.

...
TF1* L[11];
  for(int nu = 0; nu <= 10; nu++)
  {
      L[nu]= new TF1("L_0", "ROOT::Math::legendre([0],x)", -1, 1);
      L[nu]->SetParameters(nu, 0.0);
      ...
  }
...

As I understand the first parameter nu is a degree of a polynomial but the meaning of the second one 0.0 is unclear to me. Also by definition there is only one parameter :confused:

2

See the note about the minimum number of required arguments here: http://root.cern.ch/root/html/TFormula.html#TFormula:SetParameters