dna/svalue/spectrum.C

0001 // *********************************************************************
0002 // To execute this macro under ROOT after your simulation ended,
0003 //   1 - launch ROOT (usually type 'root' at your machine's prompt)
0004 //   2 - type '.X spectrum.C' at the ROOT session prompt
0005 //   3 - OR type directly 'root spectrum.C'
0006 // this will generate an output energy spectrum spectrum.txt,
0007 // according to selected statistics and distribution
0008 // (energy unit assumed by svalue example: eV)
0009 // *********************************************************************
0010
0011 {
0012 gROOT->Reset();
0013
0014 // 1) SELECT number of values to shoot
0015 int nbValues = 100;
0016 //
0017
0018 double value;
0019 TNtuple * ntuple = new TNtuple ("","","value");
0020
0021 FILE * fp = fopen("spectrum.txt","w");
0022
0023 TRandom r;
0024
0025 for (int i=0;i<nbValues;i++)
0026 {
0027 // 2) SELECT distribution
0028 //    here Gaussian with mean, sigma
0029 //    see https://root.cern.ch/doc/master/classTRandom.html
0030   value = r.Gaus(1.,0.1);
0031 //
0032   ntuple->Fill(value);
0033   fprintf(fp,"%f \n",value);
0034 }
0035 fclose(fp);
0036
0037 ntuple->Draw("value");
0038 }