/usr/include/shogun/kernel/Chi2Kernel.h is in libshogun-dev 1.1.0-4ubuntu2.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 | /*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* Written (W) 1999-2009 Soeren Sonnenburg
* Copyright (C) 1999-2009 Fraunhofer Institute FIRST and Max-Planck-Society
*/
#ifndef _CHI2KERNEL_H___
#define _CHI2KERNEL_H___
#include <shogun/lib/common.h>
#include <shogun/kernel/DotKernel.h>
#include <shogun/features/Features.h>
#include <shogun/features/SimpleFeatures.h>
namespace shogun
{
/** @brief The Chi2 kernel operating on realvalued vectors computes
* the chi-squared distance between sets of histograms.
*
* It is a very useful distance in image recognition (used to detect objects).
*
* It is defined as
* \f[
* k({\bf x},({\bf x'})= e^{-\frac{1}{width} \sum_{i=0}^{l}\frac{(x_i-x'_i)^2}{(x_i+x'_i)}}
* \f]
*
* */
class CChi2Kernel: public CDotKernel
{
void init();
public:
/** default constructor */
CChi2Kernel();
/** constructor
*
* @param size cache size
* @param width width
*/
CChi2Kernel(int32_t size, float64_t width);
/** constructor
*
* @param l features of left-hand side
* @param r features of right-hand side
* @param width width
* @param size cache size
*/
CChi2Kernel(
CSimpleFeatures<float64_t>* l, CSimpleFeatures<float64_t>* r, float64_t width, int32_t size);
virtual ~CChi2Kernel();
/** initialize kernel
*
* @param l features of left-hand side
* @param r features of right-hand side
* @return if initializing was successful
*/
virtual bool init(CFeatures* l, CFeatures* r);
/** return what type of kernel we are
*
* @return kernel type CHI2
*/
virtual EKernelType get_kernel_type() { return K_CHI2; }
/** return feature class the kernel can deal with
*
* @return feature class SIMPLE
*/
inline virtual EFeatureClass get_feature_class() { return C_SIMPLE; }
/** return feature type the kernel can deal with
*
* @return float64_t feature type
*/
virtual EFeatureType get_feature_type() { return F_DREAL; }
/** return the kernel's name
*
* @return name Chi2
*/
virtual const char* get_name() const { return "Chi2Kernel"; }
protected:
/** compute kernel function for features a and b
* idx_{a,b} denote the index of the feature vectors
* in the corresponding feature object
*
* @param idx_a index a
* @param idx_b index b
* @return computed kernel function at indices a,b
*/
virtual float64_t compute(int32_t idx_a, int32_t idx_b);
protected:
/** width */
float64_t width;
};
}
#endif /* _CHI2KERNEL_H__ */
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