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root:loadtext [2010/11/10 12:17] – nchiaproot:loadtext [2010/11/15 17:17] (current) – nchiap
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 </code> </code>
  
 +
 +=== Dynamic Branche Names ===
  
 If you do not give the structure, the first line of your file must contain the tree definition If you do not give the structure, the first line of your file must contain the tree definition
Line 27: Line 29:
   T->SetBranchAddress(col1Name.Data(),&hist1);   T->SetBranchAddress(col1Name.Data(),&hist1);
   T->SetBranchAddress(col2Name.Data(),&hist2);   T->SetBranchAddress(col2Name.Data(),&hist2);
 +</code>
 +
 +=== Dynamic Tree Structure ===
 +You can extend this idea to plot all histograms in an unknown tree.
 +The following code reads a tree form a datafile with a arbitrary number of columns
 +and creates a histogram for each of them.
 +
 +<code C++>
 +        /** Load Data into Tree **/
 +        TTree *T = new TTree("myT","data from ascii file");
 +        Long64_t nlines = T->ReadFile(filename);
 +
 +        /** Attache memory to tree **/
 +        Int_t nCols = T->GetListOfBranches()->GetEntries();
 +        std::vector<Float_t> entry(nCols, 0);
 +        for (Int_t i=0; i < nCols; i++) {
 +          TString colName = T->GetListOfBranches()->At(i)->GetName();
 +          T->SetBranchAddress(colName.Data(),&(entry[i]));
 +        }
 +
 +        /** Calculate binning **/
 +        Int_t nentries = (Int_t)T->GetEntries();
 +
 +        T->GetEntry(0);
 +        Float_t first = entry[0];
 +        T->GetEntry(1);
 +        Float_t second = entry[0];
 +        Float_t step = second-first;
 +        first = first - step/2;
 +        Float_t last = first+step*(nlines);
 +        
 +        /** Create Histograms **/
 +        TH1F *h;
 +        TObjArray histograms;
 +        for (Int_t i = 0; i < nCols; i++) {
 +          TString hName = Form("hist%d",i);
 +          if (i == 1) {
 +            h = new TH1F(hName,histTitle,nlines,first,last);
 +          } else {
 +            h = new TH1F(hName,"",nlines,first,last);
 +          }
 +          histograms.AddLast(h);
 +        }
 +
 +        /** Fill Histograms **/
 +        for (Int_t i=0;i<nentries;) {  // increment inside loop
 +          T->GetEntry(i);
 +          i++;
 +          for (Int_t col = 1; col < nCols; col++) {
 +                  h = dynamic_cast<TH1F*>(histograms[col]);
 +                  h->SetBinContent(i, entry[col]);
 +          }
 +        }       
 </code> </code>
root/loadtext.1289387859.txt.gz · Last modified: by nchiap

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