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     * Strategies for handling NaN values in rank transformations.
022     * <ul>
023     * <li>MINIMAL - NaNs are treated as minimal in the ordering, equivalent to
024     * (that is, tied with) <code>Double.NEGATIVE_INFINITY</code>.</li>
025     * <li>MAXIMAL - NaNs are treated as maximal in the ordering, equivalent to
026     * <code>Double.POSITIVE_INFINITY</code></li>
027     * <li>REMOVED - NaNs are removed before the rank transform is applied</li>
028     * <li>FIXED - NaNs are left "in place," that is the rank transformation is
029     * applied to the other elements in the input array, but the NaN elements
030     * are returned unchanged.</li>
031     * </ul>
032     *
033     * @since 2.0
034     * @version $Revision: 799857 $ $Date: 2009-08-01 09:07:12 -0400 (Sat, 01 Aug 2009) $
035     */
036    public enum NaNStrategy {
037        
038        /** NaNs are considered minimal in the ordering */
039        MINIMAL,
040        
041        /** NaNs are considered maximal in the ordering */
042        MAXIMAL,
043        
044        /** NaNs are removed before computing ranks */
045        REMOVED,
046        
047        /** NaNs are left in place */
048        FIXED
049    }