TMVA::Reader

Class Description

  The Reader class serves to use the MVAs in a specific analysis context.
  Within an event loop, a vector is filled that corresponds to the variables
  that were used to train the MVA(s) during the training stage. This vector
  is transfered to the Reader, who takes care of interpreting the weight 
  file of the MVA of choice, and to return the MVA's output. This is then 
  used by the user for further analysis.

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  Usage:
           
    // ------ before starting the event loop (eg, in the initialisation step)

    
    // create TMVA::Reader object
    
    TMVA::Reader *reader = new TMVA::Reader();    

    // create a set of variables and declare them to the reader
    // - the variable names must corresponds in name and type to 
    // those given in the weight file(s) that you use
    Float_t var1, var2, var3, var4;
    reader->AddVariable( "var1", &var1 );
    reader->AddVariable( "var2", &var2 );
    reader->AddVariable( "var3", &var3 );
    reader->AddVariable( "var4", &var4 );
      
    // book the MVA of your choice (prior training of these methods, ie, 
    // existence of the weight files is required)
    reader->BookMVA( "Fisher method",  "weights/Fisher.weights.txt"   );
    reader->BookMVA( "MLP method",     "weights/MLP.weights.txt" );
    // ... etc
    
    // ------- start your event loop

    for (Long64_t ievt=0; ievt<myTree->GetEntries();ievt++) {

      // fill vector with values of variables computed from those in the tree
      var1 = myvar1;
      var2 = myvar2;
      var3 = myvar3;
      var4 = myvar4;
            
      // retrieve the corresponding MVA output
      double mvaFi = reader->EvaluateMVA( "Fisher method" );
      double mvaNN = reader->EvaluateMVA( "MLP method"    );

      // do something with these ...., e.g., fill them into your ntuple

    } // end of event loop

    delete reader;
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  An example application of the Reader can be found in TMVA/macros/TMVApplication.C.
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