1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.math4.legacy.stat.descriptive.rank; 18 19 import org.apache.commons.math4.legacy.exception.MathIllegalArgumentException; 20 import org.apache.commons.math4.legacy.exception.NullArgumentException; 21 import org.apache.commons.math4.legacy.stat.ranking.NaNStrategy; 22 23 24 /** 25 * Returns the median of the available values. This is the same as the 50th percentile. 26 * See {@link Percentile} for a description of the algorithm used. 27 * <p> 28 * <strong>Note that this implementation is not synchronized.</strong> If 29 * multiple threads access an instance of this class concurrently, and at least 30 * one of the threads invokes the <code>increment()</code> or 31 * <code>clear()</code> method, it must be synchronized externally.</p> 32 */ 33 public class Median extends Percentile { 34 /** Fixed quantile. */ 35 private static final double FIXED_QUANTILE_50 = 50.0; 36 37 /** 38 * Default constructor. 39 */ 40 public Median() { 41 // No try-catch or advertised exception - arg is valid 42 super(FIXED_QUANTILE_50); 43 } 44 45 /** 46 * Copy constructor, creates a new {@code Median} identical. 47 * to the {@code original} 48 * 49 * @param original the {@code Median} instance to copy 50 * @throws NullArgumentException if original is null 51 */ 52 public Median(Median original) throws NullArgumentException { 53 super(original); 54 } 55 56 /** 57 * Constructs a Median with the specific {@link EstimationType}, {@link NaNStrategy} and {@link KthSelector}. 58 * 59 * @param estimationType one of the percentile {@link EstimationType estimation types} 60 * @param nanStrategy one of {@link NaNStrategy} to handle with NaNs 61 * @param kthSelector {@link KthSelector} to use for pivoting during search 62 * @throws MathIllegalArgumentException if p is not within (0,100] 63 * @throws NullArgumentException if type or NaNStrategy passed is null 64 */ 65 private Median(final EstimationType estimationType, final NaNStrategy nanStrategy, 66 final KthSelector kthSelector) 67 throws MathIllegalArgumentException { 68 super(FIXED_QUANTILE_50, estimationType, nanStrategy, kthSelector); 69 } 70 71 /** {@inheritDoc} */ 72 @Override 73 public Median withEstimationType(final EstimationType newEstimationType) { 74 return new Median(newEstimationType, getNaNStrategy(), getKthSelector()); 75 } 76 77 /** {@inheritDoc} */ 78 @Override 79 public Median withNaNStrategy(final NaNStrategy newNaNStrategy) { 80 return new Median(getEstimationType(), newNaNStrategy, getKthSelector()); 81 } 82 83 /** {@inheritDoc} */ 84 @Override 85 public Median withKthSelector(final KthSelector newKthSelector) { 86 return new Median(getEstimationType(), getNaNStrategy(), newKthSelector); 87 } 88 }