ROOT Tutorial Chapter 5.3 Modifications

[sarahf]

I was having trouble getting the code displayed in chapter 5.3 (2D histograms) of the tutorial (by Piparo, Quast, and Zeise) and couldn’t get it to work as displayed. The result of the code in the tutorial was all of the graphs stacked on top of each other, rather than on four separate pads.

I made the following modifications for it to work:
-I declared bidi_h as a pointer
-I used Draw() instead of DrawClone in each instance of DrawClone(). My code was as follows:

void Chapter5p3(){
  gStyle->SetPalette(kSunset);
  gStyle->SetOptStat(0);
  gStyle->SetOptTitle(0);

 TH2F* bidi_h = 0;
  bidi_h = new TH2F ("bidi_h","2D Histogram;Gaussian Vals;Exp Vals)",
                     10,-5,5, // x axis                                                  
                     30,0,10);//y axis                                                   


  TRandom3 rgen;
  for (int i=0;i<500000;i++)
      bidi_h->Fill(rgen.Gaus(0,2),10-rgen.Exp(4),.1); 

  auto c = new TCanvas("Canvas","Canvas",800,800);
  c->Divide(2,2);
  c->cd(1);bidi_h->Draw("Cont1");
  c->cd(2);bidi_h->Draw("Colz");
  c->cd(3);bidi_h->Draw("lego1");
  c->cd(4);bidi_h->Draw("surf3");

  //Profiles and Projections                                                             
  auto c2=new TCanvas("Canvas2","Canvas2",800,800);
  c2->Divide(2,2,0,0);
  c2->cd(1);bidi_h->ProjectionX()->Draw();
  c2->cd(2);bidi_h->ProjectionY()->Draw();
  c2->cd(3);bidi_h->ProfileX()->Draw();
  c2->cd(4);bidi_h->ProfileY()->Draw();

}

---

ROOT Version: 6.12/06
Platform: OSX
Compiler: Not Provided

---

[couet]

Thanks for the input. So that’s the ROOT primer ? can you point to some URL to make sure I will upgrade the right chapter ?

[couet]

I have modernised the macro. Thanks for your input. It is now:

// Draw a Bidimensional Histogram in many ways
// together with its profiles and projections

void macro7(){
   gStyle->SetPalette(kBird);
   gStyle->SetOptStat(0);
   gStyle->SetOptTitle(0);

   auto bidi_h = new TH2F("bidi_h","2D Histo;Gaussian Vals;Exp. Vals",
                          30,-5,5,  // X axis
                          30,0,10); // Y axis

   TRandom3 rgen;
   for (int i=0;i<500000;i++) {
      bidi_h->Fill(rgen.Gaus(0,2),10-rgen.Exp(4),.1);
   }

   auto c=new TCanvas("Canvas","Canvas",800,800);
   c->Divide(2,2);
   c->cd(1); bidi_h->Draw("Cont1");
   c->cd(2); bidi_h->Draw("Colz");
   c->cd(3); bidi_h->Draw("Lego2");
   c->cd(4); bidi_h->Draw("Surf3");

   // Profiles and Projections
   auto c2=new TCanvas("Canvas2","Canvas2",800,800);
   c2->Divide(2,2);
   c2->cd(1); bidi_h->ProjectionX()->Draw();
   c2->cd(2); bidi_h->ProjectionY()->Draw();
   c2->cd(3); bidi_h->ProfileX()->Draw();
   c2->cd(4); bidi_h->ProfileY()->Draw();
}

It will appear tomorrow on the web.