smile.math.kernel.HellingerKernel Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2015 Diego Catalano
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*******************************************************************************/
package smile.math.kernel;
import smile.math.Math;
/**
* The Hellinger Mercer Kernel.
* @author Diego Catalano
*/
public class HellingerKernel implements MercerKernel {
/**
* Constructor.
*/
public HellingerKernel() {}
@Override
public String toString() {
return "Hellinger Kernel";
}
@Override
public double k(double[] x, double[] y) {
if (x.length != y.length)
throw new IllegalArgumentException(String.format("Arrays have different length: x[%d], y[%d]", x.length, y.length));
double sum = 0;
for (int i = 0; i < x.length; i++) {
sum += Math.sqrt(x[i] * y[i]);
}
return sum;
}
}