How to access a branch with content of vector<vector<float>>?

Hello,

I’m trying to read a branch of a tree with content type of vector<vector, the original tree is created like this:

std::vector<std::vector> jtSubJetPt;
t->Branch(“jtSubJetPt”,&jets_.jtSubJetPt);

std::vector sjpt;
for (unsigned k = 0; k < jet.numberOfDaughters(); ++k) {
const reco::Candidate & dp = *jet.daughter(k);
sjpt.push_back(dp.pt());
}
jets_.jtSubJetPt.push_back(sjpt);

If I simply use draw , I can draw like this t->Draw( “jtSubJetPt[0][1]”), for all first jet’s second subjetPt, but I have no idea how to read it , I grab the idea from the tutorial: https://root.cern.ch/root/html/tutorials/tree/hvector.C.html , and write like this:

std::vector<std::vector> *subjetPt=0;
TBranch *bsubjetPt=0;
t->SetBranchAddress(“jtSubJetPt”,&subjetPt,&bsubjetPt);
for (Int_t i=0; i<nevent; i++)
{
Long64_t tentry = t->LoadTree(i);
bsubjetPt->GetEntry(tentry);
for(UInt_t j=0; j< subjetPt->size(); ++j){
hall->Fill(subjetPt->at(j));
}// end for jsize()
hfirst->Fill(subjetPt->at(0));
hsecond->Fill(subjetPt->at(1));
} // end for i<nevent

but it will return an error :

error: no matching member function for call to ‘Fill’ hall->Fill(subjetPt->at(j));
so the subjetPt->at(j) is not a float.

what could I do to correctly access the subjetPt[all][i] (all jets’ ith dauther) and save it to a new histogram or tree?
Thanks!

Try (replacing TYPE with the actual underslying type, maybe double or float).

std::vector<std::vector<TYPE> > *subjetPt=0;
TBranch *bsubjetPt=0;
t->SetBranchAddress("jtSubJetPt",&subjetPt,&bsubjetPt);
for (Int_t i=0; i<nevent; i++)
{
   Long64_t tentry = t->LoadTree(i);
   bsubjetPt->GetEntry(tentry);
   for( auto &innerVec : *subjetPt) {
      for( TYPE value : innerVec ) {
        hall->Fill( value );
      } // end for inner vector
   } // end for subjet vector.
   if (subjetPt,size() > 0 && subjetPt->at(0)->size() > 0) 
      hfirst->Fill(subjetPt->at(0)->at(0) );
} // end for i<nevent

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