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.ml.clustering;
019
020import java.util.List;
021
022/**
023 * Evaluates the quality of a set of clusters.
024 * It is assumed that
025 * <ul>
026 *  <li>rank is positive,</li>
027 *  <li>higher rank means better clustering.</li>
028 * </ul>
029 */
030@FunctionalInterface
031public interface ClusterRanking {
032    /**
033     * Computes the rank (higher is better).
034     *
035     * @param clusters Clusters to be evaluated.
036     * @return the rank of the provided {@code clusters}.
037     */
038    double compute(List<? extends Cluster<? extends Clusterable>> clusters);
039}