001 /*
002 * Java Genetic Algorithm Library (jenetics-6.2.0).
003 * Copyright (c) 2007-2021 Franz Wilhelmstötter
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * 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 * Author:
018 * Franz Wilhelmstötter (franz.wilhelmstoetter@gmail.com)
019 */
020 package io.jenetics.stat;
021
022 import static java.lang.Double.NaN;
023 import static java.util.Objects.requireNonNull;
024 import static io.jenetics.internal.util.Hashes.hash;
025
026 import java.io.Serializable;
027 import java.util.DoubleSummaryStatistics;
028 import java.util.function.ToDoubleFunction;
029 import java.util.stream.Collector;
030
031 import io.jenetics.internal.math.DoubleAdder;
032
033 /**
034 * <i>Value</i> objects which contains statistical summary information.
035 *
036 * @see java.util.DoubleSummaryStatistics
037 *
038 * @implNote
039 * This class is immutable and thread-safe.
040 *
041 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
042 * @since 3.0
043 * @version 6.0
044 */
045 public final /*record*/ class DoubleSummary implements Serializable {
046
047 private static final long serialVersionUID = 1L;
048
049 private final long _count;
050 private final double _min;
051 private final double _max;
052 private final double _sum;
053 private final double _mean;
054
055 /**
056 * Create an immutable object which contains statistical summary values.
057 *
058 * @param count the count of values recorded
059 * @param min the minimum value
060 * @param max the maximum value
061 * @param sum the sum of the recorded values
062 * @param mean the arithmetic mean of values
063 */
064 private DoubleSummary(
065 final long count,
066 final double min,
067 final double max,
068 final double sum,
069 final double mean
070 ) {
071 _count = count;
072 _min = min;
073 _max = max;
074 _sum = sum;
075 _mean = mean;
076 }
077
078 /**
079 * Returns the count of values recorded.
080 *
081 * @return the count of recorded values
082 */
083 public long count() {
084 return _count;
085 }
086
087 /**
088 * Return the minimum value recorded, or {@code Double.POSITIVE_INFINITY} if
089 * no values have been recorded.
090 *
091 * @return the minimum value, or {@code Double.POSITIVE_INFINITY} if none
092 */
093 public double min() {
094 return _min;
095 }
096
097 /**
098 * Return the maximum value recorded, or {@code Double.NEGATIVE_INFINITY} if
099 * no values have been recorded.
100 *
101 * @return the maximum value, or {@code Double.NEGATIVE_INFINITY} if none
102 */
103 public double max() {
104 return _max;
105 }
106
107 /**
108 * Return the sum of values recorded, or zero if no values have been
109 * recorded.
110 *
111 * @return the sum of values, or zero if none
112 */
113 public double sum() {
114 return _sum;
115 }
116
117 /**
118 * Return the arithmetic mean of values recorded, or zero if no values have
119 * been recorded.
120 *
121 * @return the arithmetic mean of values, or zero if none
122 */
123 public double mean() {
124 return _mean;
125 }
126
127 @Override
128 public int hashCode() {
129 return
130 hash(_count,
131 hash(_sum,
132 hash(_min,
133 hash(_max,
134 hash(_mean)))));
135 }
136
137 @Override
138 public boolean equals(final Object obj) {
139 return obj == this ||
140 obj instanceof DoubleSummary &&
141 _count == ((DoubleSummary)obj)._count &&
142 Double.compare(_sum, ((DoubleSummary)obj)._sum) == 0 &&
143 Double.compare(_min, ((DoubleSummary)obj)._min) == 0 &&
144 Double.compare(_max, ((DoubleSummary)obj)._max) == 0 &&
145 Double.compare(_mean, ((DoubleSummary)obj)._mean) == 0;
146 }
147
148 @Override
149 public String toString() {
150 return String.format(
151 "DoubleSummary[N=%d, ∧=%s, ∨=%s, Σ=%s, μ=%s]",
152 count(), min(), max(), sum(), mean()
153 );
154 }
155
156 /**
157 * Create an immutable object which contains statistical summary values.
158 *
159 * @param count the count of values recorded
160 * @param min the minimum value
161 * @param max the maximum value
162 * @param sum the sum of the recorded values
163 * @param mean the arithmetic mean of values
164 * @return an immutable object which contains statistical summary values
165 */
166 public static DoubleSummary of(
167 final long count,
168 final double min,
169 final double max,
170 final double sum,
171 final double mean
172 ) {
173 return new DoubleSummary(
174 count,
175 min,
176 max,
177 sum,
178 mean
179 );
180 }
181
182 /**
183 * Return a new value object of the statistical summary, currently
184 * represented by the {@code statistics} object.
185 *
186 * @param statistics the creating (mutable) statistics class
187 * @return the statistical moments
188 */
189 public static DoubleSummary of(final DoubleSummaryStatistics statistics) {
190 return new DoubleSummary(
191 statistics.getCount(),
192 statistics.getMin(),
193 statistics.getMax(),
194 statistics.getSum(),
195 statistics.getAverage()
196 );
197 }
198
199 /**
200 * Return a {@code Collector} which applies an double-producing mapping
201 * function to each input element, and returns summary-statistics for the
202 * resulting values.
203 *
204 * <pre>{@code
205 * final Stream<SomeObject> stream = ...
206 * final DoubleSummary summary = stream
207 * .collect(toDoubleSummary(v -> v.doubleValue()));
208 * }</pre>
209 *
210 * @param mapper a mapping function to apply to each element
211 * @param <T> the type of the input elements
212 * @return a {@code Collector} implementing the summary-statistics reduction
213 * @throws java.lang.NullPointerException if the given {@code mapper} is
214 * {@code null}
215 */
216 public static <T> Collector<T, ?, DoubleSummary>
217 toDoubleSummary(final ToDoubleFunction<? super T> mapper) {
218 requireNonNull(mapper);
219 return Collector.of(
220 DoubleSummaryStatistics::new,
221 (a, b) -> a.accept(mapper.applyAsDouble(b)),
222 (a, b) -> {a.combine(b); return a;},
223 DoubleSummary::of
224 );
225 }
226
227
228 /* *************************************************************************
229 * Some static helper methods.
230 **************************************************************************/
231
232 /**
233 * Return the minimum value of the given double array.
234 *
235 * @since 4.0
236 *
237 * @param values the double array.
238 * @return the minimum value or {@link Double#NaN} if the given array is
239 * empty.
240 * @throws NullPointerException if the given array is {@code null}.
241 */
242 public static double min(final double[] values) {
243 double min = NaN;
244 if (values.length > 0) {
245 min = values[0];
246
247 for (double value : values) {
248 if (value < min) {
249 min = value;
250 }
251 }
252 }
253
254 return min;
255 }
256
257 /**
258 * Return the maximum value of the given double array.
259 *
260 * @since 4.0
261 *
262 * @param values the double array.
263 * @return the maximum value or {@link Double#NaN} if the given array is
264 * empty.
265 * @throws NullPointerException if the given array is {@code null}.
266 */
267 public static double max(final double[] values) {
268 double max = NaN;
269 if (values.length > 0) {
270 max = values[0];
271
272 for (double value : values) {
273 if (value > max) {
274 max = value;
275 }
276 }
277 }
278
279 return max;
280 }
281
282 /**
283 * Return the sum of the given double array.
284 *
285 * @since 4.0
286 *
287 * @param values the values to sum up.
288 * @return the sum of the given {@code values}.
289 * @throws NullPointerException if the given array is {@code null}.
290 */
291 public static double sum(final double[] values) {
292 return DoubleAdder.sum(values);
293 }
294
295 /**
296 * Returns a double describing the arithmetic mean of the values, or
297 * {@link Double#NaN} if the {@code values} array is empty.
298 *
299 * @since 4.0
300 *
301 * @param values the values to calculate the mean of
302 * @return the arithmetic mean of the given {@code values} or
303 * {@link Double#NaN} if the {@code values} array is empty
304 * @throws NullPointerException if the given array is {@code null}.
305 */
306 public static double mean(final double[] values) {
307 return values.length > 0 ? sum(values)/values.length : NaN;
308 }
309
310 }
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