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; 018 019/** 020 * A strategy to pick a pivoting index of an array for doing partitioning. 021 * 022 * @see MedianOf3PivotingStrategy 023 * @see RandomPivotingStrategy 024 * @see CentralPivotingStrategy 025 * @since 4.0 026 */ 027public interface PivotingStrategy { 028 /** 029 * Find pivot index of the array so that partition and K<sup>th</sup> 030 * element selection can be made. 031 * @param work data array 032 * @param begin index of the first element of the slice 033 * @param end index after the last element of the slice 034 * @return the index of the pivot element chosen between the 035 * first and the last element of the array slice 036 * @throws IllegalArgumentException when indices exceeds range 037 */ 038 int pivotIndex(double[] work, int begin, int end); 039}