00001 // @(#)root/tmva $Id: GiniIndexWithLaplace.cxx 29122 2009-06-22 06:51:30Z brun $ 00002 // Author: Andreas Hoecker, Joerg Stelzer, Helge Voss, Kai Voss 00003 00004 /********************************************************************************** 00005 * Project: TMVA - a Root-integrated toolkit for multivariate data analysis * 00006 * Package: TMVA * 00007 * Class : TMVA::GiniIndex * 00008 * Web : http://tmva.sourceforge.net * 00009 * * 00010 * Description: Implementation of the GiniIndex With Laplace correction * 00011 * as separation criterion * 00012 * Gini(Sample M) = 1 - (c(1)/N)^2 - (c(2)/N)^2 .... - (c(k)/N)^2 * 00013 * Where: M is a smaple of whatever N elements (events) * 00014 * that belong to K different classes * 00015 * c(k) is the number of elements that belong to class k * 00016 * Laplace's correction to the prob.density c/N --> (c+1)/(N+2) * 00017 * for just Signal and Background classes this then boils down to: * 00018 * Gini(Sample) = 2(s*b+s+b+1)/(s+b+2)^2 * 00019 * * 00020 * Authors (alphabetical): * 00021 * Andreas Hoecker <Andreas.Hocker@cern.ch> - CERN, Switzerland * 00022 * Helge Voss <Helge.Voss@cern.ch> - MPI-K Heidelberg, Germany * 00023 * Kai Voss <Kai.Voss@cern.ch> - U. of Victoria, Canada * 00024 * * 00025 * Copyright (c) 2005: * 00026 * CERN, Switzerland * 00027 * U. of Victoria, Canada * 00028 * Heidelberg U., Germany * 00029 * * 00030 * Redistribution and use in source and binary forms, with or without * 00031 * modification, are permitted according to the terms listed in LICENSE * 00032 * (http://tmva.sourceforge.net/LICENSE) * 00033 **********************************************************************************/ 00034 00035 //_______________________________________________________________________ 00036 // 00037 // Implementation of the GiniIndexWithLaplace as separation criterion 00038 // 00039 //_______________________________________________________________________ 00040 00041 #include "TMVA/GiniIndexWithLaplace.h" 00042 00043 ClassImp(TMVA::GiniIndexWithLaplace) 00044 00045 //_______________________________________________________________________ 00046 Double_t TMVA::GiniIndexWithLaplace::GetSeparationIndex( const Double_t &s, const Double_t &b ) 00047 { 00048 // Gini(Sample M) = 1 - (c(1)/N)^2 - (c(2)/N)^2 .... - (c(k)/N)^2 00049 // Where: M is a smaple of whatever N elements (events) 00050 // that belong to K different classes 00051 // c(k) is the number of elements that belong to class k 00052 // Laplace's correction to the prob.density c/N --> (c+1)/(N+2) 00053 // for just Signal and Background classes this then boils down to: 00054 // Gini(Sample) = 2(s*b+s+b+1)/(s+b+2)^2 00055 00056 if (s+b <= 0) return 0; 00057 if (s<=0 || b <=0) return 0; 00058 else return (s*b+s+b+1)/(s+b+2)/(s+b+2); 00059 } 00060 00061
1.5.1