org.hipparchus.stat.descriptive.moment

Class GeometricMean

java.lang.Object

org.hipparchus.stat.descriptive.AbstractStorelessUnivariateStatistic

org.hipparchus.stat.descriptive.moment.GeometricMean

All Implemented Interfaces:

Serializable, DoubleConsumer, AggregatableStatistic<GeometricMean>, StorelessUnivariateStatistic, UnivariateStatistic, MathArrays.Function

public class GeometricMean
extends AbstractStorelessUnivariateStatistic
implements AggregatableStatistic<GeometricMean>, Serializable

Returns the geometric mean of the available values.

Uses a SumOfLogs instance to compute sum of logs and returns exp( 1/n (sum of logs) ). Therefore,

• If any of values are < 0, the result is NaN.
• If all values are non-negative and less than Double.POSITIVE_INFINITY, but at least one value is 0, the result is 0.
• If both Double.POSITIVE_INFINITY and Double.NEGATIVE_INFINITY are among the values, the result is NaN.

Note that this implementation is not synchronized. If multiple threads access an instance of this class concurrently, and at least one of the threads invokes the increment() or clear() method, it must be synchronized externally.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
GeometricMean() Create a GeometricMean instance.
GeometricMean(GeometricMean original) Copy constructor, creates a new GeometricMean identical to the original.
GeometricMean(SumOfLogs sumOfLogs) Create a GeometricMean instance using the given SumOfLogs instance.

Method Summary

Modifier and Type	Method and Description
void	aggregate(GeometricMean other) Aggregates the provided instance into this instance.
void	clear() Clears the internal state of the Statistic
GeometricMean	copy() Returns a copy of the statistic with the same internal state.
double	evaluate(double[] values, int begin, int length) Returns the geometric mean of the entries in the specified portion of the input array.
long	getN() Returns the number of values that have been added.
double	getResult() Returns the current value of the Statistic.
void	increment(double d) Updates the internal state of the statistic to reflect the addition of the new value.

Methods inherited from class org.hipparchus.stat.descriptive.AbstractStorelessUnivariateStatistic

equals, hashCode, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.hipparchus.stat.descriptive.AggregatableStatistic

aggregate, aggregate

Methods inherited from interface org.hipparchus.stat.descriptive.StorelessUnivariateStatistic

accept, incrementAll, incrementAll

Methods inherited from interface org.hipparchus.stat.descriptive.UnivariateStatistic

evaluate

Methods inherited from interface java.util.function.DoubleConsumer

andThen

Constructor Detail

GeometricMean

public GeometricMean()

Create a GeometricMean instance.

GeometricMean

public GeometricMean(SumOfLogs sumOfLogs)

Create a GeometricMean instance using the given SumOfLogs instance.

Parameters:

sumOfLogs - sum of logs instance to use for computation.

GeometricMean

public GeometricMean(GeometricMean original)
              throws NullArgumentException

Copy constructor, creates a new GeometricMean identical to the original.

Parameters:

original - the GeometricMean instance to copy

Throws:

NullArgumentException - if original is null

Method Detail

copy

public GeometricMean copy()

Returns a copy of the statistic with the same internal state.

Specified by:

copy in interface StorelessUnivariateStatistic

Specified by:

copy in interface UnivariateStatistic

Specified by:

copy in class AbstractStorelessUnivariateStatistic

Returns:

a copy of the statistic

increment

public void increment(double d)

Updates the internal state of the statistic to reflect the addition of the new value.

Specified by:

increment in interface StorelessUnivariateStatistic

Specified by:

increment in class AbstractStorelessUnivariateStatistic

Parameters:

d - the new value.

getResult

public double getResult()

Returns the current value of the Statistic.

Specified by:

getResult in interface StorelessUnivariateStatistic

Specified by:

getResult in class AbstractStorelessUnivariateStatistic

Returns:

value of the statistic, Double.NaN if it has been cleared or just instantiated.

clear

public void clear()

Clears the internal state of the Statistic

Specified by:

clear in interface StorelessUnivariateStatistic

Specified by:

clear in class AbstractStorelessUnivariateStatistic

aggregate

public void aggregate(GeometricMean other)

Aggregates the provided instance into this instance.

This method can be used to combine statistics computed over partitions or subsamples - i.e., the value of this instance after this operation should be the same as if a single statistic would have been applied over the combined dataset.

Specified by:

aggregate in interface AggregatableStatistic<GeometricMean>

Parameters:

other - the instance to aggregate into this instance

evaluate

public double evaluate(double[] values,
                       int begin,
                       int length)
                throws MathIllegalArgumentException

Returns the geometric mean of the entries in the specified portion of the input array.

See GeometricMean for details on the computing algorithm.

Specified by:

evaluate in interface StorelessUnivariateStatistic

Specified by:

evaluate in interface UnivariateStatistic

Specified by:

evaluate in interface MathArrays.Function

Parameters:

values - input array containing the values

begin - first array element to include

length - the number of elements to include

Returns:

the geometric mean or Double.NaN if length = 0 or any of the values are <= 0.

Throws:

MathIllegalArgumentException - if the input array is null or the array index parameters are not valid

See Also:

UnivariateStatistic.evaluate(double[], int, int)

getN

public long getN()

Returns the number of values that have been added.

Specified by:

getN in interface StorelessUnivariateStatistic

Returns:

the number of values.