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/*
* Java Genetic Algorithm Library (jenetics-3.4.0).
* Copyright (c) 2007-2016 Franz Wilhelmstötter
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Author:
* Franz Wilhelmstötter ([email protected])
*/
package org.jenetics.stat;
import static java.lang.Math.max;
import static java.lang.Math.min;
import static java.util.Objects.requireNonNull;
import java.util.function.IntConsumer;
import java.util.function.LongConsumer;
import java.util.function.ToLongFunction;
import java.util.stream.Collector;
/**
* A state object for collecting statistics such as count, min, max, sum, mean,
* variance, skewness and kurtosis. The design of this class is similar to the
* design of the {@link java.util.LongSummaryStatistics} class.
*
* This class is designed to work with (though does not require) streams. For
* example, you can compute moments-statistics on a stream of longs with:
*
{@code
* final LongStream stream = ...
* final LongMomentStatistics statistics = stream.collect(
* LongMomentStatistics::new,
* LongMomentStatistics::accept,
* LongMomentStatistics::combine
* );
* }
*
* For a non long stream, you can use a collector:
* {@code
* final Stream stream = ...
* final LongMomentStatistics statistics = stream
* .collect(toLongMomentStatistics(v -> v.longValue()));
* }
*
*
* Implementation note:
* This implementation is not thread safe. However, it is safe to use
* {@link #toLongMomentStatistics(ToLongFunction)} on a parallel stream, because the parallel
* implementation of {@link java.util.stream.Stream#collect Stream.collect()}
* provides the necessary partitioning, isolation, and merging of results for
* safe and efficient parallel execution.
*
* @see java.util.LongSummaryStatistics
* @see org.jenetics.stat.LongMoments
* @see
* Computing Higher-Order Moments Online
*
* @author Franz Wilhelmstötter
* @since 3.0
* @version 3.0
*/
public class LongMomentStatistics
extends MomentStatistics
implements LongConsumer, IntConsumer
{
private long _min = Long.MAX_VALUE;
private long _max = Long.MIN_VALUE;
private long _sum = 0L;
/**
* Create an empty moments object.
*/
public LongMomentStatistics() {
}
/**
* Records a new value into the moments information
*
* @param value the input {@code value}
*/
@Override
public void accept(final long value) {
super.accept(value);
_min = min(_min, value);
_max = max(_max, value);
_sum += value;
}
/**
* Records a new value into the moments information
*
* @param value the input {@code value}
*/
@Override
public void accept(final int value) {
accept((long)value);
}
/**
* Combine two {@code LongMoments} statistic objects.
*
* @param other the other {@code LongMoments} statistics to combine with
* {@code this} one.
* @return {@code this} statistics object
* @throws java.lang.NullPointerException if the other statistical summary
* is {@code null}.
*/
public LongMomentStatistics combine(final LongMomentStatistics other) {
super.combine(other);
_min = min(_min, other._min);
_max = max(_max, other._max);
_sum += other._sum;
return this;
}
/**
* Return the minimum value recorded, or {@code Long.MAX_VALUE} if no
* values have been recorded.
*
* @return the minimum value, or {@code Long.MAX_VALUE} if none
*/
public long getMin() {
return _min;
}
/**
* Return the maximum value recorded, or {@code Long.MIN_VALUE} if no
* values have been recorded.
*
* @return the maximum value, or {@code Long.MIN_VALUE} if none
*/
public long getMax() {
return _max;
}
/**
* Return the sum of values recorded, or zero if no values have been
* recorded.
*
* @return the sum of values, or zero if none
*/
public long getSum() {
return _sum;
}
@Override
public String toString() {
return String.format(
"LongMomentStatistics[N=%d, ∧=%s, ∨=%s, Σ=%s, μ=%s, s²=%s, S=%s, K=%s]",
getCount(), getMin(), getMax(), getSum(),
getMean(), getVariance(), getSkewness(), getKurtosis()
);
}
/**
* Return a {@code Collector} which applies an long-producing mapping
* function to each input element, and returns moments-statistics for the
* resulting values.
*
*
{@code
* final Stream stream = ...
* final LongMomentStatistics statistics = stream
* .collect(toLongMomentStatistics(v -> v.longValue()));
* }
*
* @param mapper a mapping function to apply to each element
* @param the type of the input elements
* @return a {@code Collector} implementing the moments-statistics reduction
* @throws java.lang.NullPointerException if the given {@code mapper} is
* {@code null}
*/
public static Collector
toLongMomentStatistics(final ToLongFunction mapper) {
requireNonNull(mapper);
return Collector.of(
LongMomentStatistics::new,
(r, t) -> r.accept(mapper.applyAsLong(t)),
LongMomentStatistics::combine
);
}
}