Package org.apache.commons.math.stat.descriptive.summary

Class SumOfLogs

java.lang.Object

org.apache.commons.math.stat.descriptive.AbstractUnivariateStatistic

org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic

org.apache.commons.math.stat.descriptive.summary.SumOfLogs

All Implemented Interfaces:

java.io.Serializable, StorelessUnivariateStatistic, UnivariateStatistic

public class SumOfLogs
extends AbstractStorelessUnivariateStatistic
implements java.io.Serializable

Returns the sum of the natural logs for this collection of values.

Uses Math.log(double) to compute the 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 Double.NEGATIVE_INFINITY.
• 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.

Version:

$Revision: 1006299 $ $Date: 2010-10-10 16:47:17 +0200 (dim. 10 oct. 2010) $

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor	Description
SumOfLogs()	Create a SumOfLogs instance
SumOfLogs(SumOfLogs original)	Copy constructor, creates a new SumOfLogs identical to the original

Method Summary

Modifier and Type	Method	Description
void	clear()	Clears the internal state of the Statistic
SumOfLogs	copy()	Returns a copy of the statistic with the same internal state.
static void	copy(SumOfLogs source, SumOfLogs dest)	Copies source to dest.
double	evaluate(double[] values, int begin, int length)	Returns the sum of the natural logs of the entries in the specified portion of the input array, or Double.NaN if the designated subarray is empty.
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.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic

equals, evaluate, hashCode, incrementAll, incrementAll

Methods inherited from class org.apache.commons.math.stat.descriptive.AbstractUnivariateStatistic

evaluate, getData, getDataRef, setData, setData, test, test

Methods inherited from class java.lang.Object

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

Constructor Detail

SumOfLogs

public SumOfLogs()

Create a SumOfLogs instance

SumOfLogs

public SumOfLogs(SumOfLogs original)

Copy constructor, creates a new SumOfLogs identical to the original

Parameters:

original - the SumOfLogs instance to copy

Method Detail

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.

getN

public long getN()

Returns the number of values that have been added.

Specified by:

getN in interface StorelessUnivariateStatistic

Returns:

the number of values.

clear

public void clear()

Clears the internal state of the Statistic

Specified by:

clear in interface StorelessUnivariateStatistic

Specified by:

clear in class AbstractStorelessUnivariateStatistic

evaluate

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

Returns the sum of the natural logs of the entries in the specified portion of the input array, or Double.NaN if the designated subarray is empty.

Throws IllegalArgumentException if the array is null.

See SumOfLogs.

Specified by:

evaluate in interface UnivariateStatistic

Overrides:

evaluate in class AbstractStorelessUnivariateStatistic

Parameters:

values - the input array

begin - index of the first array element to include

length - the number of elements to include

Returns:

the sum of the natural logs of the values or Double.NaN if length = 0

Throws:

java.lang.IllegalArgumentException - if the array is null or the array index parameters are not valid

See Also:

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

copy

public SumOfLogs 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

copy

public static void copy(SumOfLogs source,
                        SumOfLogs dest)

Copies source to dest.

Neither source nor dest can be null.

Parameters:

source - SumOfLogs to copy

dest - SumOfLogs to copy to

Throws:

java.lang.NullPointerException - if either source or dest is null