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 package org.apache.commons.math.stat.descriptive;
018
019 import org.apache.commons.math.MathRuntimeException;
020
021 /**
022 * Abstract base class for all implementations of the
023 * {@link UnivariateStatistic} interface.
024 * <p>
025 * Provides a default implementation of <code>evaluate(double[]),</code>
026 * delegating to <code>evaluate(double[], int, int)</code> in the natural way.
027 * </p>
028 * <p>
029 * Also includes a <code>test</code> method that performs generic parameter
030 * validation for the <code>evaluate</code> methods.</p>
031 *
032 * @version $Revision: 894705 $ $Date: 2009-12-30 15:24:54 -0500 (Wed, 30 Dec 2009) $
033 */
034 public abstract class AbstractUnivariateStatistic
035 implements UnivariateStatistic {
036
037 /**
038 * {@inheritDoc}
039 */
040 public double evaluate(final double[] values) {
041 test(values, 0, 0);
042 return evaluate(values, 0, values.length);
043 }
044
045 /**
046 * {@inheritDoc}
047 */
048 public abstract double evaluate(final double[] values, final int begin, final int length);
049
050 /**
051 * {@inheritDoc}
052 */
053 public abstract UnivariateStatistic copy();
054
055 /**
056 * This method is used by <code>evaluate(double[], int, int)</code> methods
057 * to verify that the input parameters designate a subarray of positive length.
058 * <p>
059 * <ul>
060 * <li>returns <code>true</code> iff the parameters designate a subarray of
061 * positive length</li>
062 * <li>throws <code>IllegalArgumentException</code> if the array is null or
063 * or the indices are invalid</li>
064 * <li>returns <code>false</li> if the array is non-null, but
065 * <code>length</code> is 0.
066 * </ul></p>
067 *
068 * @param values the input array
069 * @param begin index of the first array element to include
070 * @param length the number of elements to include
071 * @return true if the parameters are valid and designate a subarray of positive length
072 * @throws IllegalArgumentException if the indices are invalid or the array is null
073 */
074 protected boolean test(
075 final double[] values,
076 final int begin,
077 final int length) {
078
079 if (values == null) {
080 throw MathRuntimeException.createIllegalArgumentException("input values array is null");
081 }
082
083 if (begin < 0) {
084 throw MathRuntimeException.createIllegalArgumentException(
085 "start position cannot be negative ({0})", begin);
086 }
087
088 if (length < 0) {
089 throw MathRuntimeException.createIllegalArgumentException(
090 "length cannot be negative ({0})", length);
091 }
092
093 if (begin + length > values.length) {
094 throw MathRuntimeException.createIllegalArgumentException(
095 "subarray ends after array end");
096 }
097
098 if (length == 0) {
099 return false;
100 }
101
102 return true;
103
104 }
105
106 /**
107 * This method is used by <code>evaluate(double[], double[], int, int)</code> methods
108 * to verify that the begin and length parameters designate a subarray of positive length
109 * and the weights are all non-negative, non-NaN, finite, and not all zero.
110 * <p>
111 * <ul>
112 * <li>returns <code>true</code> iff the parameters designate a subarray of
113 * positive length and the weights array contains legitimate values.</li>
114 * <li>throws <code>IllegalArgumentException</code> if any of the following are true:
115 * <ul><li>the values array is null</li>
116 * <li>the weights array is null</li>
117 * <li>the weights array does not have the same length as the values array</li>
118 * <li>the weights array contains one or more infinite values</li>
119 * <li>the weights array contains one or more NaN values</li>
120 * <li>the weights array contains negative values</li>
121 * <li>the start and length arguments do not determine a valid array</li></ul>
122 * </li>
123 * <li>returns <code>false</li> if the array is non-null, but
124 * <code>length</code> is 0.
125 * </ul></p>
126 *
127 * @param values the input array
128 * @param weights the weights array
129 * @param begin index of the first array element to include
130 * @param length the number of elements to include
131 * @return true if the parameters are valid and designate a subarray of positive length
132 * @throws IllegalArgumentException if the indices are invalid or the array is null
133 * @since 2.1
134 */
135 protected boolean test(
136 final double[] values,
137 final double[] weights,
138 final int begin,
139 final int length) {
140
141 if (weights == null) {
142 throw MathRuntimeException.createIllegalArgumentException("input weights array is null");
143 }
144
145 if (weights.length != values.length) {
146 throw MathRuntimeException.createIllegalArgumentException(
147 "Different number of weights and values");
148 }
149
150 boolean containsPositiveWeight = false;
151 for (int i = begin; i < begin + length; i++) {
152 if (Double.isNaN(weights[i])) {
153 throw MathRuntimeException.createIllegalArgumentException(
154 "NaN weight at index {0}", i);
155 }
156 if (Double.isInfinite(weights[i])) {
157 throw MathRuntimeException.createIllegalArgumentException(
158 "Infinite weight at index {0}", i);
159 }
160 if (weights[i] < 0) {
161 throw MathRuntimeException.createIllegalArgumentException(
162 "negative weight {0} at index {1} ", weights[i], i);
163 }
164 if (!containsPositiveWeight && weights[i] > 0.0) {
165 containsPositiveWeight = true;
166 }
167 }
168
169 if (!containsPositiveWeight) {
170 throw MathRuntimeException.createIllegalArgumentException(
171 "weight array must contain at least one non-zero value");
172 }
173
174 return test(values, begin, length);
175 }
176 }
177