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

java.lang.Object
  extended by org.apache.commons.math.stat.descriptive.AbstractUnivariateStatistic
      extended by org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic
          extended by org.apache.commons.math.stat.descriptive.summary.SumOfLogs
All Implemented Interfaces:
Serializable, StorelessUnivariateStatistic, UnivariateStatistic

public class SumOfLogs
extends AbstractStorelessUnivariateStatistic
implements Serializable

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

Uses Math.log(double) to compute the logs. Therefore,

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: 348519 $ $Date: 2005-11-23 12:12:18 -0700 (Wed, 23 Nov 2005) $
See Also:
Serialized Form

Constructor Summary
SumOfLogs()
          Create a SumOfLogs instance
 
Method Summary
 void clear()
          Clears the internal state of the Statistic
 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
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

Method Detail

increment

public void increment(double d)
Description copied from interface: StorelessUnivariateStatistic
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.
See Also:
StorelessUnivariateStatistic.increment(double)

getResult

public double getResult()
Description copied from interface: StorelessUnivariateStatistic
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.
See Also:
StorelessUnivariateStatistic.getResult()

getN

public long getN()
Description copied from interface: StorelessUnivariateStatistic
Returns the number of values that have been added.

Specified by:
getN in interface StorelessUnivariateStatistic
Returns:
the number of values.
See Also:
StorelessUnivariateStatistic.getN()

clear

public void clear()
Description copied from interface: StorelessUnivariateStatistic
Clears the internal state of the Statistic

Specified by:
clear in interface StorelessUnivariateStatistic
Specified by:
clear in class AbstractStorelessUnivariateStatistic
See Also:
StorelessUnivariateStatistic.clear()

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:
IllegalArgumentException - if the array is null or the array index parameters are not valid
See Also:
UnivariateStatistic.evaluate(double[], int, int)


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