指针类型错误(根CERN)

Question

我正在尝试从给定的特定文件中生成直方图，但我得到了以下错误：

Error in <TTree::SetBranchAddress>: The pointer type given "Double_t" (8) does not correspond to the type needed "vector<float>" by the branch: mu_phi

我猜问题是，我试图加入的变量是以向量的形式存在的，但我不知道如何修正它。运行后的画布(无论是eta、phi、energy.)只要包含条目的数量、平均值和代表这一点的行，它们看起来都是一样的。

我是新来的，所以请容忍我。任何帮助都将不胜感激！

我的脚本(没有标题)：

void script(){
  
  TFile *file = TFile::Open("output_data.root");

  TTree* tree = (TTree*)file->Get("nominal");

  TChain* fchain = new TChain("nominal");
  fchain->Add("output_data.root");
                                                            
  Double_t mu_pt, mu_e, mu_eta, mu_phi;

   //set branches to variables
  tree->SetBranchAddress("mu_pt", &mu_pt);
  tree->SetBranchAddress("mu_e", &mu_e);
  tree->SetBranchAddress("mu_eta", &mu_eta);
  tree->SetBranchAddress("mu_phi", &mu_phi);

  TH1D *muPt = new TH1D("muPt", ";p_{T} [GeV/c];Events", 100, 0., 200.);
  TH1D *muEta = new TH1D("muEta", ";#eta;Events", 50, -3, 3);
  TH1D *muE = new TH1D("muE", ";Energy;Events", 50, 0, 200);
  TH1D *muPhi = new TH1D("muPhi", ";#phi;Events", 50, -4, 4);
  TH1D *mass = new TH1D("mass", ";mass;Events", 50, 0, 200);

  Long64_t nentries = fchain->GetEntries();

  for (int i=0; i<nentries ; i++) {

  Long64_t ientry = fchain->LoadTree(i);
  if (ientry <0 ) break;

  fchain->GetEntry(i);

  muEta->Fill(mu_eta);
  muPt->Fill(mu_pt);
  muPhi->Fill(mu_phi);
  muE->Fill(mu_e);
}
   cout << "entries = " << nentries << endl;

   TCanvas *c1 = new TCanvas("Eta","Eta",800 ,800);
   c1->cd();
   muEta->Draw();

}

根版本: 6.26/10平台:未提供编译器:未提供

我尝试将Double_t转换为vector<float>，但这给我带来了更多的错误。

error: no matching member function for call to 'Fill'
  muEta->Fill(mu_eta);
  ~~~~~~~^~~~
/snap/root-framework/838/usr/local/include/TH1.h:219:21: note: candidate function not viable: no known conversion from 'vector<float>' to 'Double_t' (aka 'double') for 1st argument
   virtual Int_t    Fill(Double_t x);
                    ^
/snap/root-framework/838/usr/local/include/TH1.h:220:21: note: candidate function not viable: requires 2 arguments, but 1 was provided
   virtual Int_t    Fill(Double_t x, Double_t w);
                    ^
/snap/root-framework/838/usr/local/include/TH1.h:221:21: note: candidate function not viable: requires 2 arguments, but 1 was provided
   virtual Int_t    Fill(const char *name, Double_t w);

可能有一种不同的方法来解决整个问题，我就是找不到。

Answer 1

看看这个参考指南，https://root.cern.ch/doc/master/classTTree.html

关于TTree::SetBranchAddress，下面是准备读取TTree不同类型分支的示例。请注意，SetBranchAddress将只将给定分支链接到特定的TTree对象；之后，为了读取给定TTree条目x的分支内容，必须调用TTree::GetEntry(x)。