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    
018    package org.apache.commons.math.stat.ranking;
019    
020    /**
021     * Interface representing a rank transformation.
022     *
023     * @since 2.0
024     * @version $Revision: 811685 $ $Date: 2009-09-05 13:36:48 -0400 (Sat, 05 Sep 2009) $
025     */
026    public interface RankingAlgorithm {
027        /**
028         * <p>Performs a rank transformation on the input data, returning an array
029         * of ranks.</p>
030         *
031         * <p>Ranks should be 1-based - that is, the smallest value
032         * returned in an array of ranks should be greater than or equal to one,
033         * rather than 0. Ranks should in general take integer values, though
034         * implementations may return averages or other floating point values
035         * to resolve ties in the input data.</p>
036         *
037         * @param data array of data to be ranked
038         * @return an array of ranks corresponding to the elements of the input array
039         */
040        double[] rank (double[] data);
041    }