How can read data from ROOT files

hungbt1908 · March 16, 2024, 1:43pm

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ROOT Version: 6.28
Platform: Window 11
Compiler: Not Provided

Dear all,
I’m a newbie in ROOT. I have a ROOT file exported from Geant4 as shown in the below image.

I wrote a script to read data to plot histograms as the attached code. But it didn’t read the data. Can anyone help me, please?

void plot()
{
    gROOT->Reset();
	gROOT->SetStyle("Plain");

	TFile* f = new TFile("output.root", "READ");

	// list all Tree and Historgram
	f->ls();

    TTree* tree = (TTree*)f->Get("DetResults0;1");

    tree->Print();
	tree->Show(10);

    double eSum;
    double eProton;
    double eAlpha;
    double eBe8;
	double eGamma;
	double eB11;
	double eB10;
	double eNeutron;
	double eOther;

	int entries;
    entries = tree->GetEntries();
    cout << "Number of entries: " << entries << endl; 

	tree->SetBranchAddress("row_wise_branch.ESum", &eSum);
    tree->SetBranchAddress("row_wise_branch.EProton", &eProton);
    tree->SetBranchAddress("row_wise_branch.EAlpha", &eAlpha);
    tree->SetBranchAddress("row_wise_branch.EBe8", &eBe8);
    tree->SetBranchAddress("row_wise_branch.EGamma", &eGamma);
	tree->SetBranchAddress("row_wise_branch.EB11", &eB11);
    tree->SetBranchAddress("row_wise_branch.EB10", &eB10);
    tree->SetBranchAddress("row_wise_branch.ENeutron", &eNeutron);
    tree->SetBranchAddress("row_wise_branch.EOther", &eOther);
    TH1D* Total_Hist = new TH1D("Total_Hist", "Total Energy Spectrum", 8000, 0., 8.);
    TH1D* Proton_Hist = new TH1D("Proton_Hist", "Proton's Energy Spectrum", 8000, 0., 8.);
    TH1D* Alpha_Hist = new TH1D("Alpha_Hist", "Alpha's Energy Spectrum", 8000, 0., 8.);
    TH1D* Be8_Hist = new TH1D("Be8_Hist", "Be8's Energy Spectrum", 8000, 0., 8.);
    TH1D* Gamma_Hits = new TH1D("Gamma_Hits", "Gamma's Energy Spectrum", 8000, 0., 8.);
    TH1D* B11_Hits = new TH1D("B11_Hits", "B11's Energy Spectrum", 8000, 0., 8.);
    TH1D* B10_Hist = new TH1D("B10_Hist", "B10's Energy Spectrum", 8000, 0., 8.);
	TH1D* Neutron_Hist = new TH1D("Neutron_Hist", "Neutron's Energy Spectrum", 8000, 0., 8.);
    TH1D* Others_Hist = new TH1D("Others_Hist", "Others Energy Spectrum", 8000, 0., 8.);

    for(int i=0; i<entries; ++i)
    {
        tree->GetEntry(i);
	
		// fill to histograms
        Total_Hist->Fill(eSum);
        Proton_Hist->Fill(eProton);
        Alpha_Hist->Fill(eAlpha);
        Be8_Hist->Fill(eBe8);
        Gamma_Hits->Fill(eGamma);
		B11_Hits->Fill(eB11);
        B10_Hist->Fill(eB10);
        Neutron_Hist->Fill(eNeutron);
        Others_Hist->Fill(eOther);
    }
}

Danilo · March 16, 2024, 2:48pm

Hi,

Welcome to the ROOT community!
I think the quickest is that you share the file with us, if possible.

Cheers,
D

hungbt1908 · March 16, 2024, 3:00pm

Thank you so much.
Here is my root file.
output.root.txt (1.4 MB)

Danilo · March 16, 2024, 3:10pm

Hi,

The file seems OK, except that the tree DetResults0 seems empty.
Example for two histos (you can easily add the rest of them!):

ROOT::RDataFrame rdf("DetResults1", "output.root");
auto hESum = rdf.Histo1D("row_wise_branch.ESum");
auto hEProton = rdf.Histo1D("row_wise_branch.EProton");
// here your other histos
TCanvas c1;
hESum->Draw();
TCanvas c2;
hEProton->Draw();

I hope this helps!

Cheers,
D

hungbt1908 · March 16, 2024, 3:50pm

Danilo:

ROOT::RDataFrame rdf("DetResults1", "output.root");
auto hESum = rdf.Histo1D("row_wise_branch.ESum");
auto hEProton = rdf.Histo1D("row_wise_branch.EProton");
// here your other histos
TCanvas c1;
hESum->Draw();
TCanvas c2;
hEProton->Draw();

Dear @Danilo
Thank you for your help. But it doesn’t work. I copied your code to my script and tried to plot the histogram. There is nothing that appeared.

Danilo · March 16, 2024, 4:55pm

Hi,

What do you mean by nothing happened? That will show 2 canvases with two histograms.

D

ajaydeo · March 16, 2024, 6:10pm

@hungbt1908

You may try replacing

TCanvas c1; hESum->Draw(); with
auto c1 = new TCanvas(); hESum->DrawClone();

and

TCanvas c2; hEProton->Draw(); with
auto c2 = new TCanvas(); hEProton->DrawClone();

Ajay

hungbt1908 · March 27, 2024, 8:20am

Thanks, @ajaydeo and @Danilo.
I have read and plotted NTuple data.
I have one more question. I would like to read row by row the NTuple data and fill them into a histogram.
How can I do it?

I have an example to read NTuple as shown below but it only worked for the newer Geant4 version.

    TFile* f = new TFile("output.root", "READ");
    TTree* tree = (TTree*)f->Get("DetResults0;1");

    double eSum;
    double eProton;
    double eAlpha;
    double eBe8;
	double eB11;
	double eB10;
	double eNeutron;
    double eGamma;
    double Other;

    tree->SetBranchAddress("ESum", &eSum);
    tree->SetBranchAddress("EProton", &eProton);
    tree->SetBranchAddress("EAlpha", &eAlpha);
    tree->SetBranchAddress("EBe8", &eBe8);
    tree->SetBranchAddress("EGamma", &eGamma);
	tree->SetBranchAddress("EB11", &eB11);
    tree->SetBranchAddress("EB10", &eB10);
    tree->SetBranchAddress("ENeutron", &eNeutron);
    tree->SetBranchAddress("EOther", &eOther);

    int entries;
    entries = tree->GetEntries();

    TH1D* Total_Hist = new TH1D("Total_Hist", "Total Energy Spectrum", 8000, 0., 8.);
    TH1D* Proton_Hist = new TH1D("Proton_Hist", "Proton's Energy Spectrum", 8000, 0., 8.);
    TH1D* Alpha_Hist = new TH1D("Alpha_Hist", "Alpha's Energy Spectrum", 8000, 0., 8.);
    TH1D* Be8_Hist = new TH1D("Be8_Hist", "Be8's Energy Spectrum", 8000, 0., 8.);
    TH1D* Gamma_Hits = new TH1D("Gamma_Hits", "Gamma's Energy Spectrum", 8000, 0., 8.);
    TH1D* B11_Hits = new TH1D("B11_Hits", "B11's Energy Spectrum", 8000, 0., 8.);
    TH1D* B10_Hist = new TH1D("B10_Hist", "B10's Energy Spectrum", 8000, 0., 8.);
	TH1D* Neutron_Hist = new TH1D("Neutron_Hist", "Neutron's Energy Spectrum", 8000, 0., 8.);
    TH1D* Others_Hist = new TH1D("Others_Hist", "Others Energy Spectrum", 8000, 0., 8.);

    for(int i=0; i<entries; ++i)
    {
        tree->GetEntry(I);
	
	    // fill to histograms
        Total_Hist->Fill(eSum);
        Proton_Hist->Fill(eProton);
        Alpha_Hist->Fill(eAlpha);
        Be8_Hist->Fill(eBe8);
        Gamma_Hits->Fill(eGamma);
	    B11_Hits->Fill(eB11);
        B10_Hist->Fill(eB10);
        Neutron_Hist->Fill(eNeutron);
        Others_Hist->Fill(eOther);
    }

system · April 10, 2024, 8:20am

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