/*
* Apache License
* Version 2.0, January 2004
* http://www.apache.org/licenses/
*
* Copyright 2013 Aurelian Tutuianu
* Copyright 2014 Aurelian Tutuianu
* Copyright 2015 Aurelian Tutuianu
* Copyright 2016 Aurelian Tutuianu
*
* 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 rapaio.core.distributions.empirical;
/**
* Triweight kernel function
*
* User: <a href="mailto:padreati@yahoo.com">Aurelian Tutuianu</a>
*/
public class KFuncTriweight implements KFunc {
private static final long serialVersionUID = 6194654792689206173L;
@Override
public double pdf(double x, double x0, double bandwidth) {
double value = Math.abs(x - x0) / bandwidth;
if (value <= 1) {
double weight = 1 - value * value;
return 35. * weight * weight * weight / 32.;
}
return 0;
}
@Override
public double minValue(double x0, double bandwidth) {
return x0 - bandwidth;
}
@Override
public double getMaxValue(double x0, double bandwidth) {
return x0 + bandwidth;
}
@Override
public String summary() {
return "KFuncTriweight";
}
}