void example(){
  
  gStyle->SetHistLineWidth(2);

  //create the tree
  TTree *tree = new TTree("exampleTree", "example");
  TObjString string1;
  TObjString string2;
  TObjString string3;
  float parameter=0;
  tree->Branch("string1", &string1);
  tree->Branch("parameter", &parameter, "parameter/F");

  gRandom->SetSeed(1);

  //fill the tree randomly (but with a fixed seed)
  
  for (unsigned i=0; i<1000; i++){
    
    if(gRandom->Rndm()<0.7)
      string1="case1";
    else if (gRandom->Rndm()<0.5)
      string1="case2";
    else if (gRandom->Rndm()<0.3)
      string1="case3";
    else if(gRandom->Rndm()<0.05)
      string1="case4";

    parameter=gRandom->Rndm();
  
    tree->Fill();

  }
  

  // draw the parameter
  tree->Draw("string1.String()>>h1");

  // now redraw but with a cut - all bins should be less or equal
  tree->Draw("string1.String()>>h2", "parameter<0.5", "same");

  //make the second histogram red
  TH1F *h2 = (TH1F*)gPad->GetListOfPrimitives()->FindObject("h2");
  if(h2)
    h2->SetLineColor(2);

  //update
  gPad->Modified();
  gPad->Update();
  


}