org.hipparchus.stat.descriptive.rank.Median Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.hipparchus.stat.descriptive.rank;
import java.io.Serializable;
import org.hipparchus.exception.MathIllegalArgumentException;
import org.hipparchus.exception.NullArgumentException;
import org.hipparchus.stat.descriptive.AbstractUnivariateStatistic;
import org.hipparchus.stat.descriptive.rank.Percentile.EstimationType;
import org.hipparchus.stat.ranking.NaNStrategy;
import org.hipparchus.util.KthSelector;
/**
* Returns the median of the available values. This is the same as the 50th percentile.
* See {@link Percentile} for a description of the algorithm used.
*
* Note that this implementation is not synchronized. If
* multiple threads access an instance of this class concurrently, and at least
* one of the threads invokes the increment() or
* clear() method, it must be synchronized externally.
*/
public class Median extends AbstractUnivariateStatistic implements Serializable {
/** Serializable version identifier */
private static final long serialVersionUID = 20150412L;
/** Fixed quantile. */
private static final double FIXED_QUANTILE_50 = 50.0;
/** The percentile impl to calculate the median. */
private final Percentile percentile;
/**
* Default constructor.
*/
public Median() {
percentile = new Percentile(FIXED_QUANTILE_50);
}
/**
* Constructs a Median with the specific {@link EstimationType},
* {@link NaNStrategy} and {@link KthSelector}.
*
* @param estimationType one of the percentile {@link EstimationType estimation types}
* @param nanStrategy one of {@link NaNStrategy} to handle with NaNs
* @param kthSelector {@link KthSelector} to use for pivoting during search
* @throws MathIllegalArgumentException if p is not within (0,100]
* @throws NullArgumentException if type or NaNStrategy passed is null
*/
private Median(final EstimationType estimationType, final NaNStrategy nanStrategy,
final KthSelector kthSelector)
throws MathIllegalArgumentException {
percentile = new Percentile(FIXED_QUANTILE_50, estimationType,
nanStrategy, kthSelector);
}
/**
* Copy constructor, creates a new {@code Median} identical
* to the {@code original}
*
* @param original the {@code Median} instance to copy
* @throws NullArgumentException if original is null
*/
Median(Median original) throws NullArgumentException {
super(original);
this.percentile = original.percentile.copy();
}
/** {@inheritDoc} */
@Override
public double evaluate(double[] values, int begin, int length)
throws MathIllegalArgumentException {
return percentile.evaluate(values, begin, length);
}
/** {@inheritDoc} */
@Override
public Median copy() {
return new Median(this);
}
/**
* Get the estimation {@link EstimationType type} used for computation.
*
* @return the {@code estimationType} set
*/
public EstimationType getEstimationType() {
return percentile.getEstimationType();
}
/**
* Build a new instance similar to the current one except for the
* {@link EstimationType estimation type}.
*
* @param newEstimationType estimation type for the new instance
* @return a new instance, with changed estimation type
* @throws NullArgumentException when newEstimationType is null
*/
public Median withEstimationType(final EstimationType newEstimationType) {
return new Median(newEstimationType,
percentile.getNaNStrategy(),
percentile.getKthSelector());
}
/**
* Get the {@link NaNStrategy NaN Handling} strategy used for computation.
* @return {@code NaN Handling} strategy set during construction
*/
public NaNStrategy getNaNStrategy() {
return percentile.getNaNStrategy();
}
/**
* Build a new instance similar to the current one except for the
* {@link NaNStrategy NaN handling} strategy.
*
* @param newNaNStrategy NaN strategy for the new instance
* @return a new instance, with changed NaN handling strategy
* @throws NullArgumentException when newNaNStrategy is null
*/
public Median withNaNStrategy(final NaNStrategy newNaNStrategy) {
return new Median(percentile.getEstimationType(),
newNaNStrategy,
percentile.getKthSelector());
}
/**
* Get the {@link KthSelector kthSelector} used for computation.
* @return the {@code kthSelector} set
*/
public KthSelector getKthSelector() {
return percentile.getKthSelector();
}
/**
* Build a new instance similar to the current one except for the
* {@link KthSelector kthSelector} instance specifically set.
*
* @param newKthSelector KthSelector for the new instance
* @return a new instance, with changed KthSelector
* @throws NullArgumentException when newKthSelector is null
*/
public Median withKthSelector(final KthSelector newKthSelector) {
return new Median(percentile.getEstimationType(),
percentile.getNaNStrategy(),
newKthSelector);
}
}