org.jenetics.stat

Class LongMomentStatistics

java.lang.Object

org.jenetics.stat.LongMomentStatistics

All Implemented Interfaces:

IntConsumer, LongConsumer

public class LongMomentStatistics
extends Object
implements LongConsumer, IntConsumer

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 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:

final LongStream stream = ... final LongMomentStatistics statistics = stream.collect( LongMomentStatistics::new, LongMomentStatistics::accept, LongMomentStatistics::combine );

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

final Stream<SomeObject> stream = ... final LongMomentStatistics statistics = stream .collect(toLongMomentStatistics(v -> v.longValue()));

Implementation note: This implementation is not thread safe. However, it is safe to use toLongMomentStatistics(ToLongFunction) 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:

3.7

Author:

Franz Wilhelmstötter

See Also:

LongSummaryStatistics, LongMoments, Computing Higher-Order Moments Online

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
void	accept(int value) Records a new value into the moments information
void	accept(long value) Records a new value into the moments information
LongMomentStatistics	combine(LongMomentStatistics other) Combine two LongMoments 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.
long	getMax() Return the maximum value recorded, or Long.MIN_VALUE if no values have been recorded.
double	getMean() Return the arithmetic mean of values recorded, or Double.NaN if no values have been recorded.
long	getMin() Return the minimum value recorded, or Long.MAX_VALUE 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.
long	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.
boolean	sameState(LongMomentStatistics other) Compares the state of two LongMomentStatistics objects.
static <T> Collector<T,?,LongMomentStatistics>	toLongMomentStatistics(ToLongFunction<? 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.LongConsumer

andThen

Methods inherited from interface java.util.function.IntConsumer

andThen

Constructor Detail

LongMomentStatistics

public LongMomentStatistics()

Create an empty moments object.

Method Detail

accept

public void accept(long value)

Records a new value into the moments information

Specified by:

accept in interface LongConsumer

Parameters:

value - the input value

accept

public void accept(int value)

Records a new value into the moments information

Specified by:

accept in interface IntConsumer

Parameters:

value - the input value

combine

public LongMomentStatistics combine(LongMomentStatistics other)

Combine two LongMoments statistic objects.

Parameters:

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

Returns:

this statistics object

Throws:

NullPointerException - if the other statistical summary is null.

getMin

public long getMin()

Return the minimum value recorded, or Long.MAX_VALUE if no values have been recorded.

Returns:

the minimum value, or Long.MAX_VALUE if none

getMax

public long getMax()

Return the maximum value recorded, or Long.MIN_VALUE if no values have been recorded.

Returns:

the maximum value, or Long.MIN_VALUE if none

getSum

public long getSum()

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

Returns:

the sum of values, or zero if none

sameState

public boolean sameState(LongMomentStatistics other)

Compares the state of two LongMomentStatistics objects. This is a replacement for the Object.equals(Object) which is not advisable to implement for this mutable object. If two object have the same state, it has still the same state when updated with the same value.

final LongMomentStatistics lms1 = ...; final LongMomentStatistics lms2 = ...; if (lms1.sameState(lms2)) { final long value = random.nextInt(1_000_000); lms1.accept(value); lms2.accept(value); assert lms1.sameState(lms2); assert lms2.sameState(lms1); assert lms1.sameState(lms1); }

Parameters:

other - the other object for the test

Returns:

true the this and the other objects have the same state, false otherwise

Since:

3.7

toString

public String toString()

Overrides:

toString in class Object

toLongMomentStatistics

public static <T> Collector<T,?,LongMomentStatistics> toLongMomentStatistics(ToLongFunction<? 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 LongMomentStatistics statistics = stream .collect(toLongMomentStatistics(v -> v.longValue()));

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