commonSense.stat.basic
Class SecondMoment
java.lang.Object
org.apache.commons.math.stat.univariate.AbstractUnivariateStatistic
org.apache.commons.math.stat.univariate.AbstractStorelessUnivariateStatistic
commonSense.stat.basic.FirstMoment
commonSense.stat.basic.SecondMoment
- All Implemented Interfaces:
- java.io.Serializable, org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic, org.apache.commons.math.stat.univariate.UnivariateStatistic
- Direct Known Subclasses:
- ThirdMoment
- public class SecondMoment
- extends FirstMoment
- implements java.io.Serializable
Computes a statistic related to the Second Central Moment. Specifically,
what is computed is the sum of squared deviations from the sample mean.
The following recursive updating formula is used:
Let
- dev = (current obs - previous mean)
- n = number of observations (including current obs)
Then
new value = old value + dev^2 * (n -1) / n.
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.
- Version:
- $Revision: 1.20 $ $Date: 2004/07/18 05:39:30 $
- See Also:
- Serialized Form
Field Summary |
protected double |
m2
second moment of values that have been added |
Constructor Summary |
SecondMoment()
Create a SecondMoment instance |
Methods inherited from class org.apache.commons.math.stat.univariate.AbstractStorelessUnivariateStatistic |
equals, evaluate, evaluate, hashCode, incrementAll, incrementAll |
Methods inherited from class org.apache.commons.math.stat.univariate.AbstractUnivariateStatistic |
test |
Methods inherited from class java.lang.Object |
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait |
m2
protected double m2
- second moment of values that have been added
SecondMoment
public SecondMoment()
- Create a SecondMoment instance
increment
public void increment(double d)
- Specified by:
increment
in interface org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic
- Overrides:
increment
in class FirstMoment
- See Also:
StorelessUnivariateStatistic.increment(double)
clear
public void clear()
- Specified by:
clear
in interface org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic
- Overrides:
clear
in class FirstMoment
- See Also:
StorelessUnivariateStatistic.clear()
getResult
public double getResult()
- Specified by:
getResult
in interface org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic
- Overrides:
getResult
in class FirstMoment
- See Also:
StorelessUnivariateStatistic.getResult()
RealJ version 3.5 2001. www.realj.com