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Added two kernels to existing SVM framework

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Histogram intersection kernel (accessible by using SVM::INTER in CV namespace as kernel_type)
Exponetial chi2 kernel (accessible by using SVM::CHI2 in CV namespace as kernel_type)

Formulars:
Exp-CHI2
k(x,y) = exp(-gamma * CHI2(x,y))
CHI2(x,y) = 1- 2* SUM_i[(xi-yi)²/(xi+yi)]

Intersec
k(x,y) = SUM_i[min(xi,yi)]
This commit is contained in:
Markus Schoeler
2013-02-14 11:30:30 +01:00
parent 956aa68fb5
commit 7cab6798c0
2 changed files with 54 additions and 3 deletions
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48
modules/ml/src/svm.cpp
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@@ -220,6 +220,8 @@ bool CvSVMKernel::create( const CvSVMParams* _params, Calc _calc_func )
calc_func = params->kernel_type == CvSVM::RBF ? &CvSVMKernel::calc_rbf :
params->kernel_type == CvSVM::POLY ? &CvSVMKernel::calc_poly :
params->kernel_type == CvSVM::SIGMOID ? &CvSVMKernel::calc_sigmoid :
params->kernel_type == CvSVM::CHI2 ? &CvSVMKernel::calc_chi2 :
params->kernel_type == CvSVM::INTER ? &CvSVMKernel::calc_intersec :
&CvSVMKernel::calc_linear;
return true;
@@ -318,6 +320,52 @@ void CvSVMKernel::calc_rbf( int vcount, int var_count, const float** vecs,
cvExp( &R, &R );
}
/// Histogram intersection kernel
void CvSVMKernel::calc_intersec( int vcount, int var_count, const float** vecs,
const float* another, Qfloat* results )
{
int j, k;
for( j = 0; j < vcount; j++ )
{
const float* sample = vecs[j];
double s = 0;
for( k = 0; k <= var_count - 4; k += 4 )
s += min(sample[k],another[k]) + min(sample[k+1],another[k+1]) +
min(sample[k+2],another[k+2]) + min(sample[k+3],another[k+3]);
for( ; k < var_count; k++ )
s += min(sample[k],another[k]);
results[j] = (Qfloat)(s);
}
}
/// Exponential chi2 kernel
void CvSVMKernel::calc_chi2( int vcount, int var_count, const float** vecs,
const float* another, Qfloat* results )
{
CvMat R = cvMat( 1, vcount, QFLOAT_TYPE, results );
double gamma = -params->gamma;
int j, k;
for( j = 0; j < vcount; j++ )
{
const float* sample = vecs[j];
double chi2 = 0;
for(k = 0 ; k < var_count; k++ )
{
double d = sample[k]*another[k];
double devisor = sample[k]+another[k];
/// if devisor == 0, the Chi2 distance would be zero, but calculation would rise an error because of deviding by zero
if (devisor != 0)
{
chi2 += d*d/devisor;
}
}
results[j] = (Qfloat) (gamma*(1.0-2*chi2));
}
if( vcount > 0 )
cvExp( &R, &R );
}
void CvSVMKernel::calc( int vcount, int var_count, const float** vecs,
const float* another, Qfloat* results )