edu.oregonstate.eecs.mcplan.ml.RadialBasisFunctionKernel.java Source code

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Here is the source code for edu.oregonstate.eecs.mcplan.ml.RadialBasisFunctionKernel.java

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/* LICENSE
Copyright (c) 2013-2016, Jesse Hostetler (jessehostetler@gmail.com)
All rights reserved.
    
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
    
1. Redistributions of source code must retain the above copyright notice,
   this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.
    
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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*/

/**
 * 
 */
package edu.oregonstate.eecs.mcplan.ml;

import org.apache.commons.math3.linear.RealVector;

/**
 * @author jhostetler
 *
 */
public class RadialBasisFunctionKernel implements KernelFunction<RealVector> {
    public final double sigma;
    private final double gamma_;

    public RadialBasisFunctionKernel(final double sigma) {
        this.sigma = sigma;
        gamma_ = -1.0 / 2 * sigma * sigma;
    }

    @Override
    public double apply(final RealVector x, final RealVector y) {
        final RealVector diff = x.subtract(y);
        final double sq_norm2 = diff.dotProduct(diff);
        return Math.exp(gamma_ * sq_norm2);
    }
}