void temp() {
  Double_t angle = TMath::Pi()/4.;
  Double_t cosphi = TMath::Cos(angle);
  Double_t sinphi = TMath::Sin(angle);
   
  TH2F *h2 = new TH2F("h2","h2",100,0,0.8,100,0,0.8);
  TRandom r;     
  for (Int_t i=0;i<1000;i++) {
    Double_t x = r.Uniform(0,1);
    Double_t y = r.Gaus(0,0.02);
    Double_t u = cosphi*x -sinphi*y;
    Double_t v = 2*sinphi*x +cosphi*y;
    h2->Fill(u,v);
  }
  TF1 *f1 = new TF1("f1","[0]+[1]*x",0,1);
  f1->SetParameters(0.,1.);
  f1->SetLineColor(kRed);
  h2->Fit(f1);
  h2->Draw();
  f1->Draw("same");
  
}