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.core.MathArrays;
020
021/**
022 * A mid point strategy based on the average of begin and end indices.
023 * @since 3.4
024 */
025public class CentralPivotingStrategy implements PivotingStrategy {
026    /**
027     * {@inheritDoc}
028     * This in particular picks a average of begin and end indices
029     * @return The index corresponding to a simple average of
030     * the first and the last element indices of the array slice
031     * @throws org.apache.commons.math4.legacy.exception.MathIllegalArgumentException MathIllegalArgumentException when indices exceeds range
032     */
033    @Override
034    public int pivotIndex(final double[] work, final int begin, final int end) {
035        MathArrays.verifyValues(work, begin, end - begin);
036        return begin + (end - begin)/2;
037    }
038}