1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.statistics.ranking;
18
19 import java.util.function.UnaryOperator;
20
21 /**
22 * Interface representing a rank transformation.
23 *
24 * @since 1.1
25 */
26 @FunctionalInterface
27 public interface RankingAlgorithm extends UnaryOperator<double[]> {
28 /**
29 * <p>Performs a rank transformation on the input data, returning an array of
30 * ranks.
31 *
32 * <p>Ranks should be 1-based: the smallest value returned in an array of ranks
33 * should be greater than or equal to one, rather than 0. Ranks should in
34 * general take integer values, though implementations may return averages or
35 * other floating point values to resolve ties in the input data.
36 *
37 * @param data Array of data to be ranked.
38 * @return an array of ranks corresponding to the elements of the input array
39 */
40 @Override
41 double[] apply(double[] data);
42 }