// fitexample.C

{
  // Step N1
  TFile *infile = new TFile("lines2.root");
  TF1 *line0 = new TF1("line0","[0]*x+[1]",0,5);
  line0->SetParameters(-1.0,10.0);
  h0->Fit("line0");
  
  // StepN2
  TF1 *fitresult = h0->GetFunction("line0");
  fitresult->GetChisquare();
  fitresult->GetNDF();
  fitresult->GetProb();

  //Step N3
  TF1 *line1 = new TF1("line1","[0]*x+[1]",0,5);
  line1->SetParameters(fitresult->GetParameter(0)+fitresult->GetParError(0),fitresult->GetParameter(1)+fitresult->GetParError(1));
  line1->SetLineStyle(2);
  line1->Draw("same");

   
  TF1 *line2 = new TF1("line2","[0]*x+[1]",0,5);
  line2->SetParameters(fitresult->GetParameter(0)+fitresult->GetParError(0),fitresult->GetParameter(1)+fitresult->GetParError(1));
  line2->SetLineStyle(2);
  line2->Draw("same");

TF1 *line3 = new TF1("line3","[0]*x+[10]",0,8);
  line2->SetParameters(fitresult->GetParameter(0)+fitresult->GetParError(0),fitresult->GetParameter(1)+fitresult->GetParError(1));
  line2->SetLineStyle(3);
  line2->Draw("same");

  // Extra STep
  TMatrixD matrix0(2,2);
  gMinuit->mnemat(matrix0.GetMatrixArray(),2);
  matrix0.Print();


  


  
  // max and min

  //TCanvas *c = new TCanvas();
  //h->Draw();
  // c->Update();
  //gPad->GetUymax();

  //Extra Step2 Parameter correlation (intercept and slope):

  c1->cd(2);

  //gMinuit->SetErrorDef(1);
  //TGraph *gr0 = (TGraph*)gMinuit->Contour(80,0,1);
  //gr0->SetLineColor(kRed);
  //gr0->Draw("alp");
  //gr0->GetXaxis()->SetTitle("parameter 0 (slope)");
  //gr0->GetYaxis()->SetTitle("parameter 1 (intercept)");
  //gr0->SetTitle("1-sigma uncertainties on fit parameters");
  //gr0->SetPoint(g->GetN(),85.74,5.34);
  // gr0->SetPoint(1,85.74,5.34);
}