TGraph *graph = new TGraph();
TCanvas *canvas = new TCanvas("canvas", "Plotting", 600, 600);


void Fill()
{
  graph->SetPoint(0, 0.01614, 6.45625E-12);
  graph->SetPoint(1, 0.10112, 4.2687E-11);
  graph->SetPoint(2, 0.74763, 3.61086E-10);
  graph->SetPoint(3, 2.39927, 1.1245e-9);
  graph->SetPoint(4, 9.84961, 4.5972e-9);

  return;
}

void Plot()
{
  extern TGraph *graph;
  graph->SetMarkerStyle(22);
  graph->SetMarkerSize(1.4);
  
  Double_t min = TMath::MinElement(graph->GetN(), graph->GetX())*0.5;
  Double_t max = TMath::MaxElement(graph->GetN(), graph->GetX())*5;

  Double_t b0 = -9;
  Double_t b1 = 1;
  Double_t b2 = -0.01;
  cout << "Minimum: " << min << "  and Maximum: " << max << endl;

  TF1 *func = new TF1("func", "TMath::Power(10,([0]+[1]*TMath::Log10(x)+[2]*TMath::Log10(x)*TMath::Log10(x)))", min, max);
  // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  // lowering min parameter doesn't change the X range of "fitline" TGraph object
  func->SetParameter(0, b0);
  func->SetParameter(1, b1);
  func->SetParameter(2, b2);
  TGraph *fitline = new TGraph(func);
  fitline->SetLineWidth(2);
  fitline->SetLineStyle(1);
  fitline->SetLineColor(1);
  
  TMultiGraph *mg = new TMultiGraph();
  mg->Add(graph, "p");
  mg->Add(fitline, "l");


  canvas->Clear();
  gPad->SetLogy(1);
  gPad->SetLogx(1);
  mg->Draw("ap");
  canvas->Update();

  return;
}