com.itemanalysis.psychometrics.kernel.SimplePluginBandwidth.java Source code

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Here is the source code for com.itemanalysis.psychometrics.kernel.SimplePluginBandwidth.java

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/*
 * Copyright 2012 J. Patrick Meyer
 *
 * 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 com.itemanalysis.psychometrics.kernel;

import org.apache.commons.math3.stat.descriptive.moment.StandardDeviation;

/**
 * See Silverman (1986, p. 45).
 *
 * Silverman, B. W. (1986). Density estimation for statistics and data analysis. Boca Raton, FL: Chapman Hall.
 *
 */
public final class SimplePluginBandwidth implements Bandwidth {

    private StandardDeviation sd = null;

    private double adjustmentFactor = 1.0;

    public SimplePluginBandwidth(StandardDeviation sd) {
        this(sd, 1.0);
    }

    public SimplePluginBandwidth(StandardDeviation sd, double adjustmentFactor) {
        this.sd = sd;
        this.adjustmentFactor = adjustmentFactor;
    }

    public double value() {
        return 1.06 * sd.getResult() * Math.pow(sd.getN(), -0.2) * adjustmentFactor;
    }

    public double getAdjustmentFactor() {
        return adjustmentFactor;
    }

}