/*

FakePhysicist.com
admin@fakephysicist.com
16 April 2017

Compile with:
g++ transformation.cpp -o transformation `root-config --cflags --libs`

*/

#include <iostream>
#include <iomanip>
#include <cmath>
#include <fstream>
#include <vector>
#include <cstring>

/****** Include the required ROOT Classes *****/
#include "TMath.h"
#include "TH1.h"
#include "TRandom.h"
#include "TStyle.h"
#include "TPad.h"
#include "TCanvas.h"
#include "TPostScript.h"
#include "TGaxis.h"
#include "TAxis.h"

using namespace std;

int main() {

  gStyle->SetPadBottomMargin(0.14);
  gStyle->SetPadTopMargin(0.09);
  gStyle->SetPadLeftMargin(0.14);
  gStyle->SetPadRightMargin(0.14);

  gStyle->SetOptFit(1111);
  gStyle->SetOptStat(0);  
  TGaxis::SetMaxDigits(3);

  double t_tau = 5.;

  TH1F * h1 = new TH1F("h1","h1",1000,0.,1.); // 1-D histogram with float
  // Arguments: name, title, bin no, xmin, xmax
  TH1F * h2 = new TH1F("h2","h2",1000,0.,70.); // 1-D histogram with float

  TCanvas *c1 = new TCanvas("c1","c1",900,1200);
  c1->Divide(1,2);		// Divide into 1x2 pads
  
  TPostScript *pss = new TPostScript("histograms.ps",111);

  pss->NewPage();
  
  for(int ij=0;ij<1000000;ij++) {	// Filling the histograms with 10000000 no of Gaussian Distribution
    double unifromR = gRandom->Uniform(); // Inform random number x
    h1->Fill(unifromR);			 // Filling Uniform]
    h2->Fill(-t_tau*TMath::Log(unifromR)); // Filling t = -t_tau*ln(x)
  }

  h1->SetTitle("Uniform Random No");
  h1->GetXaxis()->SetTitle("X");
  h1->GetXaxis()->SetTitleOffset(1.4);
  h1->GetXaxis()->CenterTitle();
  
  h2->SetTitle("Radio Active Decay");
  h2->GetXaxis()->SetTitle("Time");
  h2->GetXaxis()->SetTitleOffset(1.4);
  h2->GetXaxis()->CenterTitle();

  pss->NewPage();

  c1->cd(1);
  h1->Draw();
  h1->Fit("pol1","SQ");
  c1->cd(2);
  h2->Draw();
  gPad->SetLogy(1);
  h2->Fit("expo","SQ");
  c1->Update();

  pss->Close();

  return 0;

}