org.apache.commons.math.stat.descriptive.moment
Class ThirdMoment

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.moment.FirstMoment
              extended by org.apache.commons.math.stat.descriptive.moment.SecondMoment
                  extended by org.apache.commons.math.stat.descriptive.moment.ThirdMoment
All Implemented Interfaces:
Serializable, StorelessUnivariateStatistic, UnivariateStatistic
Direct Known Subclasses:
FourthMoment

public class ThirdMoment
extends SecondMoment
implements Serializable

Computes a statistic related to the Third Central Moment. Specifically, what is computed is the sum of cubed deviations from the sample mean.

The following recursive updating formula is used:

Let

Then

new value = old value - 3 * (dev/n) * m2 + (n-1) * (n -2) * (dev^3/n^2)

Returns Double.NaN if no data values have been added and returns 0 if there is just one value in the data set.

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
ThirdMoment()
          Create a FourthMoment instance
ThirdMoment(ThirdMoment original)
          Copy constructor, creates a new ThirdMoment identical to the original
 
Method Summary
 void clear()
          Clears the internal state of the Statistic
 ThirdMoment copy()
          Returns a copy of the statistic with the same internal state.
static void copy(ThirdMoment source, ThirdMoment dest)
          Copies source to dest.
 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.moment.SecondMoment
copy
 
Methods inherited from class org.apache.commons.math.stat.descriptive.moment.FirstMoment
copy, getN
 
Methods inherited from class org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic
equals, evaluate, evaluate, hashCode, incrementAll, incrementAll
 
Methods inherited from class org.apache.commons.math.stat.descriptive.AbstractUnivariateStatistic
evaluate, getData, setData, setData
 
Methods inherited from class java.lang.Object
getClass, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ThirdMoment

public ThirdMoment()
Create a FourthMoment instance


ThirdMoment

public ThirdMoment(ThirdMoment original)
Copy constructor, creates a new ThirdMoment identical to the original

Parameters:
original - the ThirdMoment 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
Overrides:
increment in class SecondMoment
Parameters:
d - the new value.

getResult

public double getResult()
Returns the current value of the Statistic.

Specified by:
getResult in interface StorelessUnivariateStatistic
Overrides:
getResult in class SecondMoment
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
Overrides:
clear in class SecondMoment

copy

public ThirdMoment copy()
Returns a copy of the statistic with the same internal state.

Specified by:
copy in interface StorelessUnivariateStatistic
Specified by:
copy in interface UnivariateStatistic
Overrides:
copy in class SecondMoment
Returns:
a copy of the statistic

copy

public static void copy(ThirdMoment source,
                        ThirdMoment dest)
Copies source to dest.

Neither source nor dest can be null.

Parameters:
source - ThirdMoment to copy
dest - ThirdMoment to copy to
Throws:
NullPointerException - if either source or dest is null


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