Creating random cosine angles

[Eyvaz]

Hi dear experts,
Please help.

I have plotted a 2D histogram from .txt file and now I have to generate a random cosine angle…

void CDF()
{
  TRandom2 *rand = new TRandom2(1);
  TCanvas *c1 = new TCanvas();
  TH1F *histogram = new TH1F("histogram ", " ", 10001, -1, 1);
  TH2F *hist = new TH2F("hist"," Histogram ", 10001, -1.05, 1.1, 10001, 0.0000003, 1.);
 const int length = 10001;
 double mu[length], f[length];
 double rr = 0;
 double indm = f[length];
 double M = mu[length];
 
 
  fstream file;
  file.open ("dSigma-dOmega.txt", ios::in);
  
  int loop=0;  
  while(!file.eof())
  
  {
       
      file >> mu[loop] >> f[loop];
      rr= rand-> Rndm();
      //hist->Fill(mu, f);
//   cout<<loop<<" "<<mu[loop]<<" "<<f[loop]<<" "<<rr<<endl;
loop++;
      histogram->Fill(rr);
    
       }
   
  hist->GetXaxis()->SetTitle("mu");
  hist->GetXaxis()->CenterTitle(true);
  hist->GetYaxis()->SetTitle("f");
  hist->GetYaxis()->CenterTitle(true);
  
   c1->SetLogy();
 
   hist->SetMarkerColor(35);
   hist->Draw();
   histogram->Draw();
    
   file.close();  
   } 

To complete my code I must write Wolfram Mathematica code for C++
Wolfram Mathematica code here …

While[(M = Quotient[M, 10]) != 0, While[f[[indm -= M]] > rr]; 
 indm += M];
fi = f[[indm - 1]]; 
[mu]i = [mu][[indm - 1]];
m = (rr - fi) ([mu][[indm]] - [mu]i)/(f[[indm]] - fi) + [mu]i

Best regards,

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ROOT Version: 6
Platform: Ubuntu20.10
Compiler: Not Provided

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[eguiraud]

Hi @Eyvaz ,
and welcome to the ROOT forum!

Can you please elaborate more on what exactly is not working for you? To generate a random angle it should be enough to generate a random number, possibly restrict it between 0 and 360 degrees (and then evaluate its cosine)?

Cheers,
Enrico