Hello there. I have a root file with a list of particles and I am trying to select a specific particle and fill histogram out of it. I believe I made an error on the filling part as the histogram is showing empty. I have attached the ROOT file structure in the comments section.
void KEHist()
5 {
6 TFile* file = new TFile("TargetSim_POT100.root", "READ"); //READ
7 TTree* tree = (TTree*)file->Get("DUNETargetSim");
8
9 Double_t KEnergy;
10 Char_t pid[16]; //List of particles
11
12 tree->SetBranchAddress("kineticEnergy", &KEnergy);
13 tree->SetBranchAddress("pid", &pid);
14
15 Int_t entries = tree->GetEntries("kineticEnergy");
16
17 TH1D *KEHist = new TH1D("KEHist", "Entries/POT100 - Kinetic Energy; KE [GeV]; Entries/OT100", 1000, 0, 125);
18
19 for(Int_t i = 0; i < entries; i++)
20 {
21 if (strcmp (pid, "gamma") != 0) //Selecting specific particles
22 {
23 continue;
24 }
25 else {
26 tree->GetEntry(i);
27 KEHist->Fill(KEnergy);
28 }
29 }
30
31 KEHist->Draw();
32 KEHist->SetLineColor(kRed);
33 }
I am trying to make a kinetic energy histogram for gamma particles only. Particle identifications are in the leaf “pid”.
Attach the output from: DUNETargetSim->Print();
void KEHist() {
TFile *file = TFile::Open("TargetSim_POT100.root", "READ");
if ((!file) || file->IsZombie()) { delete file; return; } // just a precaution
TTree *tree; file->GetObject("DUNETargetSim", tree);
if (!tree) { delete file; return; } // just a precaution
Double_t KEnergy;
Char_t pid;
tree->SetBranchStatus("*", 0); // disable all branches
tree->SetBranchAddress("kineticEnergy", &KEnergy);
tree->SetBranchStatus("kineticEnergy", 1); // activate this branch
tree->SetBranchAddress("pid", &pid);
tree->SetBranchStatus("pid", 1); // activate this branch
Long64_t entries = tree->GetEntries();
gROOT->cd(); // newly created histograms should go here
TH1D *KEHist = new TH1D("KEHist", "Entries/POT100 - Kinetic Energy; KE [GeV]; Entries/OT100", 1000, 0., 125.);
for(Long64_t i = 0; i < entries; i++) {
tree->GetEntry(i); // read activated (enabled) branches
if (pid != 'g') continue; // check ... DUNETargetSim->Scan("pid")
KEHist->Fill(KEnergy);
}
KEHist->SetLineColor(kRed);
KEHist->Draw();
delete file; // automatically deletes "tree", too
}
1 Like
Thank you very much for improving the code.
First, I figured out the error in my code.
for(Int_t i = 0; i < entries; i++)
{ tree->GetEntry(i); //This one was below the if statement
if (strcmp (pid, "gamma") != 0) //Selecting specific particle
{
continue;
}
else {
KEHist->Fill(KEnergy);
}
}
Second, I tried to run your code which showed this error message.
I think it could be because there is no particle “g” when I scanned the “pid”.
if (pid != "g") continue; // check ... DUNETargetSim->Scan("pid")
KEHist->Fill(KEnergy);
When I changed this to “gamma”, it asked me to use strncmp function.
I got my solution. However, if you have time can you please explain to me the second error part and how to deal with it.
Check what values the “pid” contains: DUNETargetSim->Scan("pid");
@pcanal That’s a bit strange because the output of “DUNETargetSim->Print();” suggested “pid” was a single “Char_t” value.
@TheScientist Try with:
// ...
Char_t pid[32];
// ...
if (strcmp(pid, "gamma")) continue;
// ...
1 Like
pcanal
July 29, 2021, 9:31pm
10
Indeed, the output of Print seems incomplete/incorrect for this case.
