void test() {
  vector < float > X, Xerr;
  vector < float > Y, Yerr;
  for(int i=0 ; i<10 ; ++i) {
    X.push_back(i*0.1); Xerr.push_back(1.);
    Y.push_back(i*2.2); Yerr.push_back(1.);
  }
  TGraphErrors *g = new TGraphErrors(X.size(), &(X[0]), &(Y[0]), &(Xerr[0]), &(Yerr[0]));
  g->SetMarkerStyle(20);
  g->SetMarkerSize(1.2);
  g->Draw();
  TF1 *f = new TF1("f","pol1",0.,1.);
  g->Fit("f","R");
  gStyle->SetOptFit(true);
  
  TPaveStats *stat1 = (TPaveStats*)g->FindObject("stats");
  stat1->SetX1NDC(0.35);
  stat1->SetY1NDC(0.40);
  stat1->SetX2NDC(0.65);
  stat1->SetY2NDC(0.60);
  gPad->Modified();

}