PDEFoamTarget.cxx

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// @(#)root/tmva $Id$
// Author: Tancredi Carli, Dominik Dannheim, Alexander Voigt

/**********************************************************************************
 * Project: TMVA - a Root-integrated toolkit for multivariate data analysis       *
 * Package: TMVA                                                                  *
 * Classes: PDEFoamTarget                                                         *
 * Web    : http://tmva.sourceforge.net                                           *
 *                                                                                *
 * Description:                                                                   *
 *      Implementation.                                                           *
 *                                                                                *
 * Authors (alphabetical):                                                        *
 *      Tancredi Carli   - CERN, Switzerland                                      *
 *      Dominik Dannheim - CERN, Switzerland                                      *
 *      S. Jadach        - Institute of Nuclear Physics, Cracow, Poland           *
 *      Alexander Voigt  - TU Dresden, Germany                                    *
 *      Peter Speckmayer - CERN, Switzerland                                      *
 *                                                                                *
 * Copyright (c) 2008, 2010:                                                      *
 *      CERN, Switzerland                                                         *
 *      MPI-K Heidelberg, Germany                                                 *
 *                                                                                *
 * Redistribution and use in source and binary forms, with or without             *
 * modification, are permitted according to the terms listed in LICENSE           *
 * (http://tmva.sourceforge.net/LICENSE)                                          *
 **********************************************************************************/

/*! \class TMVA::PDEFoamTarget
\ingroup TMVA
This PDEFoam variant stores in every cell the average target
fTarget (see the Constructor) as well as the statistical error on
the target fTarget.  It therefore acts as a target estimator.  It
should be booked together with the PDEFoamTargetDensity density
estimator, which returns the target fTarget density at a given
phase space point during the foam build-up.
*/

#include "TMVA/PDEFoamTarget.h"

#include "TMVA/Event.h"
#include "TMVA/MsgLogger.h"
#include "TMVA/PDEFoam.h"
#include "TMVA/PDEFoamCell.h"
#include "TMVA/PDEFoamKernelBase.h"
#include "TMVA/Types.h"

#include "TMath.h"

#include "Rtypes.h"

ClassImp(TMVA::PDEFoamTarget);

////////////////////////////////////////////////////////////////////////////////
/// Default constructor for streamer, user should not use it.

TMVA::PDEFoamTarget::PDEFoamTarget()
: PDEFoam()
   , fTarget(0)
{
}

////////////////////////////////////////////////////////////////////////////////
/// User constructor
///
/// Parameters:
///
/// - name - name of PDEFoam object
///
/// - target - target number to range-search for

TMVA::PDEFoamTarget::PDEFoamTarget(const TString& name, UInt_t target)
   : PDEFoam(name)
   , fTarget(target)
{
}

////////////////////////////////////////////////////////////////////////////////
/// Copy Constructor  NOT IMPLEMENTED (NEVER USED)

TMVA::PDEFoamTarget::PDEFoamTarget(const PDEFoamTarget &from)
   : PDEFoam(from)
   , fTarget(from.fTarget)
{
   Log() << kFATAL << "COPY CONSTRUCTOR NOT IMPLEMENTED" << Endl;
}

////////////////////////////////////////////////////////////////////////////////
/// This function fills an event into the discriminant PDEFoam.  The
/// weight 'wt' is filled into cell element 0 if the event is of
/// class 'fTarget', and filled into cell element 1 otherwise.

void TMVA::PDEFoamTarget::FillFoamCells(const Event* ev, Float_t wt)
{
   // find corresponding foam cell
   std::vector<Float_t> values  = ev->GetValues();
   std::vector<Float_t> tvalues = VarTransform(values);
   std::vector<Float_t> targets = ev->GetTargets();
   PDEFoamCell *cell = FindCell(tvalues);

   // 0. Element: Number of events
   // 1. Element: Target 0
   SetCellElement(cell, 0, GetCellElement(cell, 0) + wt);
   SetCellElement(cell, 1, GetCellElement(cell, 1) + wt * targets.at(fTarget));
}

////////////////////////////////////////////////////////////////////////////////
/// Calculate average cell target in every cell and save them to the
/// cell.  Cell element 0 will contain the average target and cell
/// element 1 will contain the error on the target.

void TMVA::PDEFoamTarget::Finalize()
{
   // loop over cells
   for (Long_t iCell = 0; iCell <= fLastCe; iCell++) {
      if (!(fCells[iCell]->GetStat()))
         continue;

      Double_t n_ev  = GetCellElement(fCells[iCell], 0); // get number of events
      Double_t tar   = GetCellElement(fCells[iCell], 1); // get sum of targets

      if (n_ev > 0) {
         SetCellElement(fCells[iCell], 0, tar / n_ev); // set average target
         SetCellElement(fCells[iCell], 1, tar / TMath::Sqrt(n_ev)); // set error on average target
      } else {
         SetCellElement(fCells[iCell], 0, 0.0);  // set mean target
         SetCellElement(fCells[iCell], 1, -1);   // set mean target error
      }
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Returns true, if the target error equals -1, as set in
/// Finalize() in case of no events in the cell

Bool_t TMVA::PDEFoamTarget::CellValueIsUndefined(PDEFoamCell* cell)
{
   return GetCellValue(cell, kValueError) == -1;
}

////////////////////////////////////////////////////////////////////////////////
/// This function finds the cell, which corresponds to the given
/// untransformed event vector 'xvec' and return its value, which is
/// given by the parameter 'cv'.
///
/// If cv == kValue, it is checked wether the cell value is
/// undefined.  If this is the case, then the mean of the neighbor's
/// target values is returned, using GetAverageNeighborsValue().

Float_t TMVA::PDEFoamTarget::GetCellValue(const std::vector<Float_t> &xvec, ECellValue cv, PDEFoamKernelBase *kernel)
{
   std::vector<Float_t> txvec(VarTransform(xvec));
   PDEFoamCell *cell = FindCell(txvec);

   if (!CellValueIsUndefined(cell)) {
      // cell is not empty
      if (kernel == NULL)
         return GetCellValue(cell, cv);
      else
         return kernel->Estimate(this, txvec, cv);
   } else
      // cell is empty -> calc average target of neighbor cells
      return GetAverageNeighborsValue(txvec, kValue);
}

////////////////////////////////////////////////////////////////////////////////
/// This function returns the average value 'cv' of only nearest
/// neighbor cells.  It is used in cases, where empty cells shall
/// not be evaluated.
///
/// Parameters:
/// - txvec - event vector, transformed into foam coordinates [0, 1]
/// - cv - cell value, see definition of ECellValue

Float_t TMVA::PDEFoamTarget::GetAverageNeighborsValue(std::vector<Float_t> &txvec,
                                                      ECellValue cv)
{
   const Float_t xoffset = 1.e-6;
   Float_t norm   = 0; // normalisation
   Float_t result = 0; // return value

   PDEFoamCell *cell = FindCell(txvec); // find corresponding cell
   PDEFoamVect cellSize(GetTotDim());
   PDEFoamVect cellPosi(GetTotDim());
   cell->GetHcub(cellPosi, cellSize); // get cell coordinates

   // loop over all dimensions and find neighbor cells
   for (Int_t dim = 0; dim < GetTotDim(); dim++) {
      std::vector<Float_t> ntxvec(txvec);
      PDEFoamCell* left_cell  = 0; // left cell
      PDEFoamCell* right_cell = 0; // right cell

      // get left cell
      ntxvec[dim] = cellPosi[dim] - xoffset;
      left_cell = FindCell(ntxvec);
      if (!CellValueIsUndefined(left_cell)) {
         // if left cell is not empty, take its value
         result += GetCellValue(left_cell, cv);
         norm++;
      }
      // get right cell
      ntxvec[dim] = cellPosi[dim] + cellSize[dim] + xoffset;
      right_cell = FindCell(ntxvec);
      if (!CellValueIsUndefined(right_cell)) {
         // if right cell is not empty, take its value
         result += GetCellValue(right_cell, cv);
         norm++;
      }
   }
   if (norm > 0)  result /= norm; // calc average target
   else         result = 0;     // return null if all neighbors are empty

   return result;
}