Alexander Leinoff
efb64f2c7d
Unnecessary end of line whitespace is generally frowned upon. In addition some editors remove end of line whitespace automatically, making diffs hard to read. This commit removes all trailing witespaces. Using some sed magic in bash: find . -name "*.*" -type f -print0 | xargs gsed -i 's/[ \t]*$//'
66 lines
1.8 KiB
C++
66 lines
1.8 KiB
C++
/**
|
|
* @file epanechnikov_kernel.cpp
|
|
* @author Neil Slagle
|
|
*
|
|
* Implementation of non-template Epanechnikov kernels.
|
|
*/
|
|
#include "epanechnikov_kernel.hpp"
|
|
|
|
#include <boost/math/special_functions/gamma.hpp>
|
|
|
|
using namespace mlpack;
|
|
using namespace mlpack::kernel;
|
|
|
|
/**
|
|
* Compute the normalizer of this Epanechnikov kernel for the given dimension.
|
|
*
|
|
* @param dimension Dimension to calculate the normalizer for.
|
|
*/
|
|
double EpanechnikovKernel::Normalizer(const size_t dimension)
|
|
{
|
|
return 2.0 * pow(bandwidth, (double) dimension) *
|
|
std::pow(M_PI, dimension / 2.0) /
|
|
(boost::math::tgamma(dimension / 2.0 + 1.0) * (dimension + 2.0));
|
|
}
|
|
|
|
/**
|
|
* Evaluate the kernel not for two points but for a numerical value.
|
|
*/
|
|
double EpanechnikovKernel::Evaluate(const double distance) const
|
|
{
|
|
return std::max(0.0, 1 - std::pow(distance, 2.0) * inverseBandwidthSquared);
|
|
}
|
|
|
|
/**
|
|
* Evaluate gradient of the kernel not for two points
|
|
* but for a numerical value.
|
|
*/
|
|
double EpanechnikovKernel::Gradient(const double distance) const {
|
|
if (std::abs(bandwidth) < std::abs(distance)) {
|
|
return 0;
|
|
} else if (std::abs(bandwidth > std::abs(distance))) {
|
|
return -2 * inverseBandwidthSquared * distance;
|
|
} else {
|
|
// The gradient doesn't exist.
|
|
return arma::datum::nan;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Evaluate gradient of the kernel not for two points
|
|
* but for a numerical value.
|
|
*/
|
|
double EpanechnikovKernel::GradientForSquaredDistance(const double
|
|
distanceSquared) const {
|
|
double bandwidthSquared = bandwidth * bandwidth;
|
|
if (distanceSquared < bandwidthSquared) {
|
|
return -1 * inverseBandwidthSquared;
|
|
} else if (distanceSquared > bandwidthSquared &&
|
|
distanceSquared >= 0) {
|
|
return 0;
|
|
} else {
|
|
// The gradient doesn't exist.
|
|
return arma::datum::nan;
|
|
}
|
|
}
|