/* In this ROOT function we generate a distribution according to sin(x) between 0 and pi using the ROOT function method

To run do:
root 
.L boxgenerate.C+ 
boxgenerate(10000)
*/

// include C++ STL headers 
#include <iostream>

using namespace std;

// ROOT library obejcts
#include <TF1.h> // 1d function class
#include <TH1.h> // 1d histogram classes
#include <TStyle.h>  // style object
#include <TMath.h>   // math functions
#include <TCanvas.h> // canvas object

void rootfuncgenerate(Int_t nEvents) 
{
  cout << "Generating " << nEvents << " events" << endl << endl;

  // create histogram objects
  TH1F* hSin = new TH1F("hSin", "ROOT func generated sin(x) distribution", 
			100, 0, TMath::Pi());
  
  // make a loop for the number of events
  TF1* sinFunc = new TF1("sinFunc", "sin(x)", 0, TMath::Pi());

  for(Int_t n = 0; n < nEvents; n++) {
    
    if((n+1)%1000==0)
      cout << "event " << n+1 << endl;
    
    hSin->Fill(sinFunc->GetRandom()); // fill our sin dist histogram
  }
  
  gStyle->SetOptStat(1111);
  gStyle->SetOptFit(1111);

  // create canvas for hSin
  TCanvas* c1 = new TCanvas("c1", "sin canvas", 900, 600);
  hSin->SetMinimum(0);
  hSin->Draw();

  // creat 1d function
  TF1* func = new TF1("func", "[0]*sin(x)", 0, TMath::Pi());
  func->SetParameter(0, 10);
  func->SetLineColor(kRed);
  hSin->Fit(func);

  c1->SaveAs("sinx_rootfunc.gif");
}

// Questions:
// What is the efficiency of the generation?
// does this agree with theory?