h1ReadAndDraw.C File Reference

Detailed Description

Read a 1-D histogram from a ROOT File and draw it.

We attach (or generate) the ROOT file in $ROOTSYS/tutorials/hsimple.root or $PWD/hsimple.root We draw one histogram in different formats.

 
#include "TInterpreter.h"
#include "TCanvas.h"
#include "TSystem.h"
#include "TFile.h"
#include "TH2.h"
#include "TNtuple.h"
#include "TPaveLabel.h"
#include "TPaveText.h"
#include "TFrame.h"
#include "TSystem.h"
#include "TInterpreter.h"
 
void h1ReadAndDraw()
{
   // Fetch and open the hsimple.root File
   TFile *example = TFile::Open(gROOT->GetTutorialDir() + "/hsimple.root");
 
   example->ls(); // Show the file contents
   // Get the histogram from the ROOT File
   TH1 *hpx = nullptr; // pointer to base class TH1 is enough
   example->GetObject("hpx", hpx);
 
   TCanvas *c1 = new TCanvas("c1","Histogram Drawing Options",200,10,700,900);
   TPad *pad1 = new TPad("pad1",
      "The pad with the function",0.03,0.62,0.50,0.92);
   TPad *pad2 = new TPad("pad2",
      "The pad with the histogram",0.51,0.62,0.98,0.92);
   TPad *pad3 = new TPad("pad3",
      "The pad with the histogram",0.03,0.02,0.97,0.57);
   pad1->Draw();
   pad2->Draw();
   pad3->Draw();
 
   // Draw a global picture title
   TPaveLabel *title = new TPaveLabel(0.1,0.94,0.9,0.98,
                    "Drawing options for one dimensional histograms");
   title->SetTextFont(52);
   title->Draw();
 
   // Draw histogram hpx in first pad with the default option.
   pad1->cd();
   pad1->GetFrame()->SetFillColor(18);
   hpx->SetFillColor(45);
   hpx->DrawCopy();
   TPaveLabel *label1 = new TPaveLabel(-3.5,700,-1,800,"Default option");
   label1->Draw();
 
   // Draw hpx as a lego. Clicking on the lego area will show
   // a "transparent cube" to guide you rotating the lego in real time.
   pad2->cd();
   hpx->DrawCopy("lego1");
   TPaveLabel *label2 = new TPaveLabel(-0.72,0.74,-0.22,0.88,"option Lego1");
   label2->Draw();
   TPaveLabel *label2a = new TPaveLabel(-0.93,-1.08,0.25,-0.92,
      "Click on lego to rotate");
   label2a->Draw();
 
   // Draw hpx with its errors and a marker.
   pad3->cd();
   pad3->SetGridx();
   pad3->SetGridy();
   hpx->SetMarkerStyle(21);
   hpx->Draw("e1p");
   TPaveLabel *label3 = new TPaveLabel(2,600,3.5,650,"option e1p");
   label3->Draw();
 
   // The following illustrates how to add comments using a PaveText.
   // Attributes of text/lines/boxes added to a PaveText can be modified.
   // The AddText function returns a pointer to the added object.
   TPaveText *pave = new TPaveText(-3.78,500,-1.2,750);
   TText *t1=pave->AddText("You can move");
   t1->SetTextColor(4);
   t1->SetTextSize(0.05);
   pave->AddText("Title and Stats pads");
   pave->AddText("X and Y axis");
   pave->AddText("You can modify bin contents");
   pave->Draw();
   c1->Update();
}

Author

Rene Brun

Definition in file h1ReadAndDraw.C.