 ROOT   Reference Guide TMVA::GiniIndex Class Reference

Implementation of the GiniIndex as separation criterion.

Large Gini Indices (maximum 0.5) mean , that the sample is well mixed (same amount of signal and bkg) bkg.

Small Indices mean, well separated.

#### General definition:

$Gini(Sample M) = 1 - (\frac{c(1)}{N})^2 - (\frac{c(2)}{N})^2 .... - (\frac{c(k)}{N})^2$

Where:

$$M$$ is a sample of whatever $$N$$ elements (events) that belong to $$K$$ different classes.

$$c(k)$$ is the number of elements that belong to class $$k$$ for just Signal and Background classes this boils down to:

$Gini(Sample) = \frac{2sb}{(s+b)^2}$

Definition at line 63 of file GiniIndex.h.

## Public Member Functions

GiniIndex ()

GiniIndex (const GiniIndex &g)

virtual ~GiniIndex ()

virtual Double_t GetSeparationIndex (const Double_t s, const Double_t b)
what we use here is 2*Gini. More... Public Member Functions inherited from TMVA::SeparationBase
SeparationBase ()
Constructor. More...

SeparationBase (const SeparationBase &s)
Copy constructor. More...

virtual ~SeparationBase ()

const TStringGetName ()

virtual Double_t GetSeparationGain (const Double_t nSelS, const Double_t nSelB, const Double_t nTotS, const Double_t nTotB)
Separation Gain: the measure of how the quality of separation of the sample increases by splitting the sample e.g. More...

virtual Double_t GetSeparationIndex (const Double_t s, const Double_t b)=0 Protected Attributes inherited from TMVA::SeparationBase
TString fName

Double_t fPrecisionCut

#include <TMVA/GiniIndex.h>

Inheritance diagram for TMVA::GiniIndex:
[legend]

## ◆ GiniIndex() [1/2]

 TMVA::GiniIndex::GiniIndex ( )
inline

Definition at line 68 of file GiniIndex.h.

## ◆ GiniIndex() [2/2]

 TMVA::GiniIndex::GiniIndex ( const GiniIndex & g )
inline

Definition at line 71 of file GiniIndex.h.

## ◆ ~GiniIndex()

 virtual TMVA::GiniIndex::~GiniIndex ( )
inlinevirtual

Definition at line 74 of file GiniIndex.h.

## ◆ GetSeparationIndex()

 Double_t TMVA::GiniIndex::GetSeparationIndex ( const Double_t s, const Double_t b )
virtual

what we use here is 2*Gini.

. as for the later use the factor 2 is irrelevant and hence I'd like to save this calculation

Implements TMVA::SeparationBase.

Definition at line 76 of file GiniIndex.cxx.

Libraries for TMVA::GiniIndex: [legend]

The documentation for this class was generated from the following files: