001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.math4.legacy.stat.descriptive.rank; 018 019import org.apache.commons.math4.legacy.exception.MathIllegalArgumentException; 020import org.apache.commons.math4.legacy.exception.NullArgumentException; 021import org.apache.commons.math4.legacy.stat.ranking.NaNStrategy; 022 023 024/** 025 * Returns the median of the available values. This is the same as the 50th percentile. 026 * See {@link Percentile} for a description of the algorithm used. 027 * <p> 028 * <strong>Note that this implementation is not synchronized.</strong> If 029 * multiple threads access an instance of this class concurrently, and at least 030 * one of the threads invokes the <code>increment()</code> or 031 * <code>clear()</code> method, it must be synchronized externally.</p> 032 */ 033public class Median extends Percentile { 034 /** Fixed quantile. */ 035 private static final double FIXED_QUANTILE_50 = 50.0; 036 037 /** 038 * Default constructor. 039 */ 040 public Median() { 041 // No try-catch or advertised exception - arg is valid 042 super(FIXED_QUANTILE_50); 043 } 044 045 /** 046 * Copy constructor, creates a new {@code Median} identical. 047 * to the {@code original} 048 * 049 * @param original the {@code Median} instance to copy 050 * @throws NullArgumentException if original is null 051 */ 052 public Median(Median original) throws NullArgumentException { 053 super(original); 054 } 055 056 /** 057 * Constructs a Median with the specific {@link EstimationType}, {@link NaNStrategy} and {@link KthSelector}. 058 * 059 * @param estimationType one of the percentile {@link EstimationType estimation types} 060 * @param nanStrategy one of {@link NaNStrategy} to handle with NaNs 061 * @param kthSelector {@link KthSelector} to use for pivoting during search 062 * @throws MathIllegalArgumentException if p is not within (0,100] 063 * @throws NullArgumentException if type or NaNStrategy passed is null 064 */ 065 private Median(final EstimationType estimationType, final NaNStrategy nanStrategy, 066 final KthSelector kthSelector) 067 throws MathIllegalArgumentException { 068 super(FIXED_QUANTILE_50, estimationType, nanStrategy, kthSelector); 069 } 070 071 /** {@inheritDoc} */ 072 @Override 073 public Median withEstimationType(final EstimationType newEstimationType) { 074 return new Median(newEstimationType, getNaNStrategy(), getKthSelector()); 075 } 076 077 /** {@inheritDoc} */ 078 @Override 079 public Median withNaNStrategy(final NaNStrategy newNaNStrategy) { 080 return new Median(getEstimationType(), newNaNStrategy, getKthSelector()); 081 } 082 083 /** {@inheritDoc} */ 084 @Override 085 public Median withKthSelector(final KthSelector newKthSelector) { 086 return new Median(getEstimationType(), getNaNStrategy(), newKthSelector); 087 } 088}