TiesStrategy.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.math3.stat.ranking;

/**
 * Strategies for handling tied values in rank transformations.
 * <ul>
 * <li>SEQUENTIAL - Ties are assigned ranks in order of occurrence in the original array,
 * for example (1,3,4,3) is ranked as (1,2,4,3)</li>
 * <li>MINIMUM - Tied values are assigned the minimum applicable rank, or the rank
 * of the first occurrence. For example, (1,3,4,3) is ranked as (1,2,4,2)</li>
 * <li>MAXIMUM - Tied values are assigned the maximum applicable rank, or the rank
 * of the last occurrence. For example, (1,3,4,3) is ranked as (1,3,4,3)</li>
 * <li>AVERAGE - Tied values are assigned the average of the applicable ranks.
 * For example, (1,3,4,3) is ranked as (1,2.5,4,2.5)</li>
 * <li>RANDOM - Tied values are assigned a random integer rank from among the
 * applicable values. The assigned rank will always be an integer, (inclusively)
 * between the values returned by the MINIMUM and MAXIMUM strategies.</li>
 * </ul>
 *
 * @since 2.0
 */
public enum TiesStrategy {

    /** Ties assigned sequential ranks in order of occurrence */
    SEQUENTIAL,

    /** Ties get the minimum applicable rank */
    MINIMUM,

    /** Ties get the maximum applicable rank */
    MAXIMUM,

    /** Ties get the average of applicable ranks */
    AVERAGE,

    /** Ties get a random integral value from among applicable ranks */
    RANDOM
}