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--- root:loadtext [2010/11/09 16:33] – created nchiap
+++ root:loadtext [2010/11/10 12:17] – nchiap
@@ Line 2: / Line 2: @@
 To read data from a text file into a tree all you need are the following two lines
 <code C++>
-  TTree *myTree = new TTree("ntuple","data from ascii file");
+  TTree *myTree = new TTree("mytree","data from ascii file");
   Long64_t nlines = myTree->ReadFile(filename,"col1:col2:col3");
+</code>
+If you do not give the structure, the first line of your file must contain the tree definition
+<code text input.csv>
+bin:hist1:hist2
+12 13
+[...]
+</code>
+To use this tree you then need to get the branch names
+<code C++>
+  TTree *myTree = new TTree("mytree","data from ascii file");
+  Long64_t nlines = myTree->ReadFile(filename);
+  TString col0Name = T->GetListOfBranches()->At(0)->GetName();
+  TString col1Name = T->GetListOfBranches()->At(1)->GetName();
+  TString col2Name = T->GetListOfBranches()->At(2)->GetName();
+  Float_t bin,hist1,hist2;
+  T->SetBranchAddress(col0Name.Data(),&bin);
+  T->SetBranchAddress(col1Name.Data(),&hist1);
+  T->SetBranchAddress(col2Name.Data(),&hist2);
 </code>

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