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 */
017package org.apache.commons.statistics.ranking;
018
019/**
020 * Strategies for handling {@link Double#NaN NaN} values in rank transformations.
021 *
022 * @since 1.1
023 */
024public enum NaNStrategy {
025
026    /**
027     * NaNs are considered minimal in the ordering, equivalent to (that is, tied
028     * with) {@linkplain Double#NEGATIVE_INFINITY negative infinity}.
029     */
030    MINIMAL,
031
032    /**
033     * NaNs are considered maximal in the ordering, equivalent to (that is, tied
034     * with) {@linkplain Double#POSITIVE_INFINITY positive infinity}.
035     */
036    MAXIMAL,
037
038    /** NaNs are removed before rank transform is applied. */
039    REMOVED,
040
041    /**
042     * NaNs are left fixed "in place", that is the rank transformation is applied to
043     * the other elements in the input array, but the NaN elements are returned
044     * unchanged.
045     */
046    FIXED,
047
048    /** NaNs result in an exception. */
049    FAILED
050}