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GiniIndex.cxx
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// @(#)root/tmva $Id$
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// Author: Andreas Hoecker, Joerg Stelzer, Helge Voss, Kai Voss
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/**********************************************************************************
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* Project: TMVA - a Root-integrated toolkit for multivariate data analysis *
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* Package: TMVA *
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* Class : TMVA::GiniIndex *
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* *
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* *
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* Description: Implementation of the GiniIndex as separation criterion *
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* Large Gini Indices (maximum 0.5) mean , that the sample is well *
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* mixed (same amount of signal and bkg) *
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* bkg. Small Indices mean, well separated. *
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* general definition: *
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* Gini(Sample M) = 1 - (c(1)/N)^2 - (c(2)/N)^2 .... - (c(k)/N)^2 *
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* Where: M is a sample of whatever N elements (events) *
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* that belong to K different classes *
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* c(k) is the number of elements that belong to class k *
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* for just Signal and Background classes this boils down to: *
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* Gini(Sample) = 2s*b/(s+b)^2 *
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* *
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* Authors (alphabetical): *
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* Andreas Hoecker <Andreas.Hocker@cern.ch> - CERN, Switzerland *
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* Helge Voss <Helge.Voss@cern.ch> - MPI-K Heidelberg, Germany *
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* Kai Voss <Kai.Voss@cern.ch> - U. of Victoria, Canada *
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* *
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* Copyright (c) 2005: *
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* CERN, Switzerland *
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* U. of Victoria, Canada *
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* Heidelberg U., Germany *
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* *
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* Redistribution and use in source and binary forms, with or without *
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* modification, are permitted according to the terms listed in LICENSE *
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* (see tmva/doc/LICENSE) *
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**********************************************************************************/
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/*! \class TMVA::GiniIndex
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\ingroup TMVA
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Implementation of the GiniIndex as separation criterion.
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Large Gini Indices (maximum 0.5) mean , that the sample is well mixed (same
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amount of signal and bkg) bkg.
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Small Indices mean, well separated.
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#### General definition:
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\f[
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Gini(Sample M) = 1 - (\frac{c(1)}{N})^2 - (\frac{c(2)}{N})^2 .... - (\frac{c(k)}{N})^2
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\f]
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Where:
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\f$ M \f$ is a sample of whatever \f$ N \f$ elements (events) that belong
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to \f$ K \f$ different classes.
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\f$ c(k) \f$ is the number of elements that belong to class \f$ k \f$ for just
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Signal and Background classes this boils down to:
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\f[
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Gini(Sample) = \frac{2sb}{(s+b)^2}
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\f]
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*/
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#include "
TMVA/GiniIndex.h
"
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#include "
Rtypes.h
"
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ClassImp
(
TMVA::GiniIndex
);
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////////////////////////////////////////////////////////////////////////////////
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/// what we use here is 2*Gini.. as for the later use the factor
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/// 2 is irrelevant and hence I'd like to save this calculation
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Double_t
TMVA::GiniIndex::GetSeparationIndex
(
const
Double_t
s,
const
Double_t
b
)
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{
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if
(s+
b
<= 0)
return
0;
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if
(s<=0 ||
b
<=0)
return
0;
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// else return s*b/(s+b)/(s+b);
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else
return
2*s*
b
/(s+
b
)/(s+
b
);
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}
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GiniIndex.h
b
#define b(i)
Definition
RSha256.hxx:100
Rtypes.h
ClassImp
#define ClassImp(name)
Definition
Rtypes.h:382
TMVA::GiniIndex
Implementation of the GiniIndex as separation criterion.
Definition
GiniIndex.h:63
TMVA::GiniIndex::GetSeparationIndex
virtual Double_t GetSeparationIndex(const Double_t s, const Double_t b)
what we use here is 2*Gini.
Definition
GiniIndex.cxx:76
double
tmva
tmva
src
GiniIndex.cxx
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