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 */
017
018package org.apache.commons.math4.stat.ranking;
019
020/**
021 * Interface representing a rank transformation.
022 *
023 * @since 2.0
024 */
025public interface RankingAlgorithm {
026    /**
027     * <p>Performs a rank transformation on the input data, returning an array
028     * of ranks.</p>
029     *
030     * <p>Ranks should be 1-based - that is, the smallest value
031     * returned in an array of ranks should be greater than or equal to one,
032     * rather than 0. Ranks should in general take integer values, though
033     * implementations may return averages or other floating point values
034     * to resolve ties in the input data.</p>
035     *
036     * @param data array of data to be ranked
037     * @return an array of ranks corresponding to the elements of the input array
038     */
039    double[] rank (double[] data);
040}