//---------------------------------------------------------------------------
//
// This root macro file is used for basic fitting of a TGraph object.
//
// Mar 2024
//---------------------------------------------------------------------------

void fitter(){
  // values
  const int n = 5;
  double x[n] = {1,2,3,4,5};
  double y[n] = {10, 7, 6, 5, 3};

  // construct TGraph and draw it
  TGraph *gr = new TGraph(n, x, y);
  gr->SetMarkerStyle(20);
  gr->SetMarkerSize(1);
  gr->Draw("AP");

  // user defined fit function
  TF1 *f1 = new TF1("fitfun", "[0]*exp(-[1]*x)", 0, 80);
  f1->SetParameter(0, 1);
  f1->SetParameter(1, 1);

  gr->Fit(f1);
}