LoadTree如何在root中工作

How does LoadTree work in root?

本文关键字：工作 root LoadTree      更新时间：2023-10-16

我写了以下代码来在一些树中读取(这只是裸露的骨架，它正在开发中(：

~~included headers here
using namespace std;
void reconstruction::readtest(){
  TFile *file = TFile::Open("file.root");
  TTree* comp_tree = (TTree*)file->Get("_compress_tree");
  TTree* compch_tree = (TTree*)file->Get("_compress_ch");
  TChain* compchain = new TChain("_compress_tree");
  compchain->Add("file.root");
  TChain* chchain = new TChain("_compress_ch");
  chchain->Add("file.root");

  TH2D *hist = new TH2D("hist","hist",100,0,0.05,100,0,60);                                                                                        
  Double_t _compression, _compressionU, _compressionV, _compressionY, _ch_compression;
  Int_t _ch;
  comp_tree->SetBranchAddress("_compression",&_compression);
  comp_tree->SetBranchAddress("_compressionU",&_compressionU);
  comp_tree->SetBranchAddress("_compressionV",&_compressionV);
  comp_tree->SetBranchAddress("_compressionY",&_compressionY);
  compch_tree->SetBranchAddress("_ch_compression",&_ch_compression);
  compch_tree->SetBranchAddress("_ch",&_ch);
   TH1D *comp = new TH1D("comp","_compression",100,0,0.05);
   TH1D *comp_ch = new TH1D("comp_ch","channel compression",100,0,0.02);
  Long64_t nentries = compchain->GetEntries();
  for (int i=0; i<2 ; i++) {
    Long64_t ientry = LoadTree(i);
    if (ientry <0 ) break;
  compchain->GetEntry(i);
  cout << "compression = " << _compression << endl;
  cout << "compression_ch = " << _ch_compression << endl;
  comp->Fill(_compression);
  comp_ch->Fill(_ch_compression);
}
   cout << "entries = " << nentries << endl;
   TCanvas *cans = new TCanvas("cans","xxx",800,400);
   cans->Divide(2,1);
   cans->cd(1);
   comp_ch->Draw();
   cans->cd(2);
   comp->Draw();
}

我收到以下错误消息：

readtest.C:51:20: error: use of undeclared identifier 'LoadTree'
Long64_t ientry = LoadTree(i);

通过谷歌搜索，我开始明白我需要： some_class::LoadTree但我完全不确定哪个类以及如何做到这一点......

我

只是想要一种方法来循环所有事件，并制作我的历史！

而不是

Long64_t ientry = LoadTree(i);

用

Long64_t ientry = compchain->LoadTree(i);

或

Long64_t ientry = chchain->LoadTree(i);

(这取决于您的哪个对象 - compchain 或chchain - 您想使用 LoadTree(( 方法 - 我想这对compchain来说也是如此。

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