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.exception.util.LocalizedFormats;
020    import org.apache.commons.math.exception.NullArgumentException;
021    import org.apache.commons.math.util.MathUtils;
022    
023    /**
024     *
025     * Abstract implementation of the {@link StorelessUnivariateStatistic} interface.
026     * <p>
027     * Provides default <code>evaluate()</code> and <code>incrementAll(double[])<code>
028     * implementations.</p>
029     * <p>
030     * <strong>Note that these implementations are not synchronized.</strong></p>
031     *
032     * @version $Revision: 983921 $ $Date: 2010-08-10 12:46:06 +0200 (mar. 10 ao??t 2010) $
033     */
034    public abstract class AbstractStorelessUnivariateStatistic
035        extends AbstractUnivariateStatistic
036        implements StorelessUnivariateStatistic {
037    
038        /**
039         * This default implementation calls {@link #clear}, then invokes
040         * {@link #increment} in a loop over the the input array, and then uses
041         * {@link #getResult} to compute the return value.
042         * <p>
043         * Note that this implementation changes the internal state of the
044         * statistic.  Its side effects are the same as invoking {@link #clear} and
045         * then {@link #incrementAll(double[])}.</p>
046         * <p>
047         * Implementations may override this method with a more efficient and
048         * possibly more accurate implementation that works directly with the
049         * input array.</p>
050         * <p>
051         * If the array is null, an IllegalArgumentException is thrown.</p>
052         * @param values input array
053         * @return the value of the statistic applied to the input array
054         * @see org.apache.commons.math.stat.descriptive.UnivariateStatistic#evaluate(double[])
055         */
056        @Override
057        public double evaluate(final double[] values) {
058            if (values == null) {
059                throw new NullArgumentException(LocalizedFormats.INPUT_ARRAY);
060            }
061            return evaluate(values, 0, values.length);
062        }
063    
064        /**
065         * This default implementation calls {@link #clear}, then invokes
066         * {@link #increment} in a loop over the specified portion of the input
067         * array, and then uses {@link #getResult} to compute the return value.
068         * <p>
069         * Note that this implementation changes the internal state of the
070         * statistic.  Its side effects are the same as invoking {@link #clear} and
071         * then {@link #incrementAll(double[], int, int)}.</p>
072         * <p>
073         * Implementations may override this method with a more efficient and
074         * possibly more accurate implementation that works directly with the
075         * input array.</p>
076         * <p>
077         * If the array is null or the index parameters are not valid, an
078         * IllegalArgumentException is thrown.</p>
079         * @param values the input array
080         * @param begin the index of the first element to include
081         * @param length the number of elements to include
082         * @return the value of the statistic applied to the included array entries
083         * @see org.apache.commons.math.stat.descriptive.UnivariateStatistic#evaluate(double[], int, int)
084         */
085        @Override
086        public double evaluate(final double[] values, final int begin, final int length) {
087            if (test(values, begin, length)) {
088                clear();
089                incrementAll(values, begin, length);
090            }
091            return getResult();
092        }
093    
094        /**
095         * {@inheritDoc}
096         */
097        @Override
098        public abstract StorelessUnivariateStatistic copy();
099    
100        /**
101         * {@inheritDoc}
102         */
103        public abstract void clear();
104    
105        /**
106         * {@inheritDoc}
107         */
108        public abstract double getResult();
109    
110        /**
111         * {@inheritDoc}
112         */
113        public abstract void increment(final double d);
114    
115        /**
116         * This default implementation just calls {@link #increment} in a loop over
117         * the input array.
118         * <p>
119         * Throws IllegalArgumentException if the input values array is null.</p>
120         *
121         * @param values values to add
122         * @throws IllegalArgumentException if values is null
123         * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#incrementAll(double[])
124         */
125        public void incrementAll(double[] values) {
126            if (values == null) {
127                throw new NullArgumentException(LocalizedFormats.INPUT_ARRAY);
128            }
129            incrementAll(values, 0, values.length);
130        }
131    
132        /**
133         * This default implementation just calls {@link #increment} in a loop over
134         * the specified portion of the input array.
135         * <p>
136         * Throws IllegalArgumentException if the input values array is null.</p>
137         *
138         * @param values  array holding values to add
139         * @param begin   index of the first array element to add
140         * @param length  number of array elements to add
141         * @throws IllegalArgumentException if values is null
142         * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#incrementAll(double[], int, int)
143         */
144        public void incrementAll(double[] values, int begin, int length) {
145            if (test(values, begin, length)) {
146                int k = begin + length;
147                for (int i = begin; i < k; i++) {
148                    increment(values[i]);
149                }
150            }
151        }
152    
153        /**
154         * Returns true iff <code>object</code> is an
155         * <code>AbstractStorelessUnivariateStatistic</code> returning the same
156         * values as this for <code>getResult()</code> and <code>getN()</code>
157         * @param object object to test equality against.
158         * @return true if object returns the same value as this
159         */
160        @Override
161        public boolean equals(Object object) {
162            if (object == this ) {
163                return true;
164            }
165           if (object instanceof AbstractStorelessUnivariateStatistic == false) {
166                return false;
167            }
168            AbstractStorelessUnivariateStatistic stat = (AbstractStorelessUnivariateStatistic) object;
169            return MathUtils.equalsIncludingNaN(stat.getResult(), this.getResult()) &&
170                   MathUtils.equalsIncludingNaN(stat.getN(), this.getN());
171        }
172    
173        /**
174         * Returns hash code based on getResult() and getN()
175         *
176         * @return hash code
177         */
178        @Override
179        public int hashCode() {
180            return 31* (31 + MathUtils.hash(getResult())) + MathUtils.hash(getN());
181        }
182    
183    }