Dear Rooters,
I am trying to figure out how to read a single element, row, or column of data
from 2D array in a TTree without reading the entire array for each event. As
shown in the example below, I can read any element from the array I wish, but
by using the command b->GetEvent(i), the entire array is read. Is there a way
to avoid reading the entire event/array?
Macro to create sample data set.
{
gROOT->Reset();
Float_t adc[10][10];
TFile *file=new TFile("adc.root","RECREATE");
TTree *tree=new TTree("tree","Testing still");
tree->Branch("adc",adc,"adc[10][10]/F");
for (Int_t k=0; k<150; k++) {
for(Int_t j=0; j<10; j++) {
for(Int_t i=0; i<10; i++) adc[i][j]=k*100+j*10+i;
}
tree->Fill();
}
tree->Write();
tree->Print();
file->Close();
}
Macro to read a element [1][1] from each event of the data set.
{
gROOT->Reset();
Float_t na[10][10];
TFile file("adc.root");
TBranch *b = tree->GetBranch("adc");
TLeaf *l = b->GetLeaf("adc");
tree->SetBranchAddress("adc",&na);
for (Int_t i=0; i<150; i++) {
b->GetEvent(i);
printf("na[1][1] = %f, ",na[1][1]);
}
}
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