ChiSquareDistance.cpp

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00001 /*
00002  * This program is free software; you can redistribute it and/or modify
00003  * it under the terms of the GNU General Public License as published by
00004  * the Free Software Foundation; either version 3 of the License, or
00005  * (at your option) any later version.
00006  *
00007  * Written (W) 2008-2009 Christian Gehl
00008  * Copyright (C) 2008-2009 Fraunhofer Institute FIRST
00009  */
00010 
00011 #include <shogun/lib/config.h>
00012 #include <shogun/lib/common.h>
00013 #include <shogun/io/SGIO.h>
00014 #include <shogun/distance/ChiSquareDistance.h>
00015 #include <shogun/features/Features.h>
00016 
00017 using namespace shogun;
00018 
00019 CChiSquareDistance::CChiSquareDistance() : CDenseDistance<float64_t>()
00020 {
00021 }
00022 
00023 CChiSquareDistance::CChiSquareDistance(CDenseFeatures<float64_t>* l, CDenseFeatures<float64_t>* r)
00024 : CDenseDistance<float64_t>()
00025 {
00026     init(l, r);
00027 }
00028 
00029 CChiSquareDistance::~CChiSquareDistance()
00030 {
00031     cleanup();
00032 }
00033 
00034 bool CChiSquareDistance::init(CFeatures* l, CFeatures* r)
00035 {
00036     bool result=CDenseDistance<float64_t>::init(l,r);
00037 
00038     return result;
00039 }
00040 
00041 void CChiSquareDistance::cleanup()
00042 {
00043 }
00044 
00045 float64_t CChiSquareDistance::compute(int32_t idx_a, int32_t idx_b)
00046 {
00047     int32_t alen, blen;
00048     bool afree, bfree;
00049 
00050     float64_t* avec=
00051         ((CDenseFeatures<float64_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
00052     float64_t* bvec=
00053         ((CDenseFeatures<float64_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);
00054 
00055     ASSERT(alen==blen);
00056 
00057     float64_t absTmp = 0;
00058     float64_t result=0;
00059     {
00060         for (int32_t i=0; i<alen; i++)
00061         {
00062             absTmp=fabs(avec[i])+fabs(bvec[i]);
00063             if(absTmp!=0)
00064                 result+=pow((avec[i]-bvec[i]),2)/absTmp;
00065         }
00066 
00067     }
00068 
00069     ((CDenseFeatures<float64_t>*) lhs)->free_feature_vector(avec, idx_a, afree);
00070     ((CDenseFeatures<float64_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree);
00071 
00072     return result;
00073 }
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