mk3pl4hmerge(char* filename, float seed=1234)
{
  // Open/create the histogram file
  histf = new TFile(filename,"RECREATE");

  TH1F* hist[10];
  TH2F* hist2[10];
  TNtuple* ntuple;

  histf->cd();
  hist[0]= new TH1F("h1d1", "h1d1", 5, -0.5, 4.5);
  hist2[0]= new TH2F("h2d1", "h2d1", 3, -0.5, 2.5, 3, -0.5, 2.5);
  ntuple = new TNtuple("ntuple", "event", "evtno:x:y");

  histf->mkdir("dir1"); histf->cd("dir1");
  hist[1]= new TH1F("h1d2", "h1d2", 5, -0.5, 4.5);
  hist2[1]= new TH2F("h2d2", "h2d2", 3, -0.5, 2.5, 3, -0.5, 2.5);

  // fill
  const Int_t Try=10;
  gRandom->SetSeed(seed);

 for ( Int_t i=0; i<Try; i++) {
   hist[0]->Fill(gRandom->Integer(5));
   hist[1]->Fill(gRandom->Integer(5));
   hist2[0]->Fill(gRandom->Integer(3), gRandom->Integer(3));
   hist2[1]->Fill(gRandom->Integer(3), gRandom->Integer(3));
   ntuple->Fill(i, gRandom->Integer(5), gRandom->Integer(5));
 }

  // Close the histogram file
  histf -> Write();
  histf -> Close();
}