Java List Median getMedian(List list)

Description

get Median

License

Open Source License

Declaration

public static Object getMedian(List<Comparable> list) 

Method Source Code

//package com.java2s;
/*/*from www. j a v  a2  s . c  o  m*/
 * Copyright (c) 2010 The Broad Institute
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
 * THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

import java.util.*;

public class Main {
    public static Object getMedian(List<Comparable> list) {
        return orderStatisticSearch((int) Math.ceil(list.size() / 2), list);
    }

    public static Comparable orderStatisticSearch(int orderStat, List<Comparable> list) {
        // this finds the order statistic of the list (kth largest element)
        // the list is assumed *not* to be sorted

        final Comparable x = list.get(orderStat);
        ListIterator iterator = list.listIterator();
        ArrayList lessThanX = new ArrayList();
        ArrayList equalToX = new ArrayList();
        ArrayList greaterThanX = new ArrayList();

        for (Comparable y : list) {
            if (x.compareTo(y) > 0) {
                lessThanX.add(y);
            } else if (x.compareTo(y) < 0) {
                greaterThanX.add(y);
            } else
                equalToX.add(y);
        }

        if (lessThanX.size() > orderStat)
            return orderStatisticSearch(orderStat, lessThanX);
        else if (lessThanX.size() + equalToX.size() >= orderStat)
            return orderStat;
        else
            return orderStatisticSearch(orderStat - lessThanX.size() - equalToX.size(), greaterThanX);

    }
}

Related

1. calculateMAD(List values, Number median)
2. calculateMedian(List values)
3. calculateMedian(List values, boolean copyAndSort)
4. getGeneMedian(final List doubleArray)
5. getMedian(Collection list)
6. getMedian(List numbers)
7. getMedian(List results)
8. getMedianValue(List nums)
9. median(ArrayList values)