org.jenetics.stat

Class DoubleMomentStatistics

java.lang.Object

org.jenetics.stat.DoubleMomentStatistics

All Implemented Interfaces:

DoubleConsumer

public class DoubleMomentStatistics
extends Object
implements DoubleConsumer

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 DoubleSummaryStatistics class.

This class is designed to work with (though does not require) streams. For example, you can compute moments-statistics on a stream of doubles with:

final DoubleStream stream = ... final DoubleMomentStatistics statistics = stream.collect( DoubleMomentStatistics::new, DoubleMomentStatistics::accept, DoubleMomentStatistics::combine );

For a non double stream, you can use a collector:

final Stream<SomeObject> stream = ... final DoubleMomentStatistics statistics = stream .collect(toDoubleMomentStatistics(v -> v.doubleValue()));

Implementation note: This implementation is not thread safe. However, it is safe to use toDoubleMomentStatistics(ToDoubleFunction) on a parallel stream, because the parallel implementation of Stream.collect() provides the necessary partitioning, isolation, and merging of results for safe and efficient parallel execution.

Since:

3.0

Version:

3.0 — $Date: 2014-12-28 $

Author:

Franz Wilhelmstötter

See Also:

DoubleSummaryStatistics, DoubleMoments, Computing Higher-Order Moments Online

Constructor Summary

Constructors

Constructor and Description
DoubleMomentStatistics() Create an empty moments object.

Method Summary

Modifier and Type	Method and Description
void	accept(double value) Records a new value into the moments information
DoubleMomentStatistics	combine(DoubleMomentStatistics other) Combine two DoubleMoments statistic objects.
long	getCount() Returns the count of values recorded.
double	getKurtosis() Return the kurtosis of values recorded, or Double.NaN if less than four values have been recorded.
double	getMax() Return the maximum value recorded, or Double.NEGATIVE_INFINITY if no values have been recorded.
double	getMean() Return the arithmetic mean of values recorded, or Double.NaN if no values have been recorded.
double	getMin() Return the minimum value recorded, or Double.POSITIVE_INFINITY if no values have been recorded.
double	getSkewness() Return the skewness of values recorded, or Double.NaN if less than two values have been recorded.
double	getSum() Return the sum of values recorded, or zero if no values have been recorded.
double	getVariance() Return the variance of values recorded, or Double.NaN if no values have been recorded.
static <T> Collector<T,?,DoubleMomentStatistics>	toDoubleMomentStatistics(ToDoubleFunction<? super T> mapper) Return a Collector which applies an long-producing mapping function to each input element, and returns moments-statistics for the resulting values.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.function.DoubleConsumer

andThen

Constructor Detail

DoubleMomentStatistics

public DoubleMomentStatistics()

Create an empty moments object.

Method Detail

accept

public void accept(double value)

Records a new value into the moments information

Specified by:

accept in interface DoubleConsumer

Parameters:

value - the input value

combine

public DoubleMomentStatistics combine(DoubleMomentStatistics other)

Combine two DoubleMoments statistic objects.

Parameters:

other - the other DoubleMoments statistics to combine with this one.

Returns:

this statistics object

Throws:

NullPointerException - if the other statistical summary is null.

getMin

public double getMin()

Return the minimum value recorded, or Double.POSITIVE_INFINITY if no values have been recorded.

Returns:

the minimum value, or Double.POSITIVE_INFINITY if none

getMax

public double getMax()

Return the maximum value recorded, or Double.NEGATIVE_INFINITY if no values have been recorded.

Returns:

the maximum value, or Double.NEGATIVE_INFINITY if none

getSum

public double getSum()

Return the sum of values recorded, or zero if no values have been recorded.

Returns:

the sum of values, or zero if none

toString

public String toString()

Overrides:

toString in class Object

toDoubleMomentStatistics

public static <T> Collector<T,?,DoubleMomentStatistics> toDoubleMomentStatistics(ToDoubleFunction<? super T> mapper)

Return a Collector which applies an long-producing mapping function to each input element, and returns moments-statistics for the resulting values.

final Stream<SomeObject> stream = ... final DoubleMomentStatistics statistics = stream .collect(toDoubleMomentStatistics(v -> v.doubleValue()));

Type Parameters:

T - the type of the input elements

Parameters:

mapper - a mapping function to apply to each element

Returns:

a Collector implementing the moments-statistics reduction

Throws:

NullPointerException - if the given mapper is null

getCount

public long getCount()

Returns the count of values recorded.

Returns:

the count of recorded values

getMean

public double getMean()

Return the arithmetic mean of values recorded, or Double.NaN if no values have been recorded.

Returns:

the arithmetic mean of values, or zero if none

getVariance

public double getVariance()

Return the variance of values recorded, or Double.NaN if no values have been recorded.

Returns:

the variance of values, or NaN if none

getSkewness

public double getSkewness()

Return the skewness of values recorded, or Double.NaN if less than two values have been recorded.

Returns:

the skewness of values, or NaN if less than two values have been recorded

See Also:

Skewness

getKurtosis

public double getKurtosis()

Return the kurtosis of values recorded, or Double.NaN if less than four values have been recorded.

Returns:

the kurtosis of values, or NaN if less than four values have been recorded

See Also:

Kurtosis