commonSense.stat.basic
Class FirstMoment

java.lang.Object
  org.apache.commons.math.stat.univariate.AbstractUnivariateStatistic
      org.apache.commons.math.stat.univariate.AbstractStorelessUnivariateStatistic
          commonSense.stat.basic.FirstMoment

All Implemented Interfaces:

java.io.Serializable, org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic, org.apache.commons.math.stat.univariate.UnivariateStatistic

Direct Known Subclasses:

SecondMoment

public class FirstMoment

extends org.apache.commons.math.stat.univariate.AbstractStorelessUnivariateStatistic

implements java.io.Serializable

Computes the first moment (arithmetic mean). Uses the definitional formula:

mean = sum(x_i) / n

where n is the number of observations.

To limit numeric errors, the value of the statistic is computed using the following recursive updating algorithm:

1. Initialize m = the first value
2. For each additional value, update using
   m = m + (new value - m) / (number of observations)

Returns Double.NaN if the dataset is empty.

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	dev Deviation of most recently added value from previous first moment.
protected double	m1 First moment of values that have been added
protected long	n Count of values that have been added
protected double	nDev Deviation of most recently added value from previous first moment, normalized by previous sample size.

Constructor Summary

FirstMoment()
Create a FirstMoment instance

Method Summary

void	clear()
long	getN()
double	getResult()
void	increment(double d)

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

Field Detail

n

protected long n

Count of values that have been added

m1

protected double m1

First moment of values that have been added

dev

protected double dev

Deviation of most recently added value from previous first moment. Retained to prevent repeated computation in higher order moments.

nDev

protected double nDev

Deviation of most recently added value from previous first moment, normalized by previous sample size. Retained to prevent repeated computation in higher order moments

Constructor Detail

FirstMoment

public FirstMoment()

Create a FirstMoment instance

Method Detail

increment

public void increment(double d)

Specified by:

increment in interface org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic

See Also:

StorelessUnivariateStatistic.increment(double)

clear

public void clear()

Specified by:

clear in interface org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic

See Also:

StorelessUnivariateStatistic.clear()

getResult

public double getResult()

Specified by:

getResult in interface org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic

See Also:

StorelessUnivariateStatistic.getResult()

getN

public long getN()

Specified by:

getN in interface org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic

See Also:

StorelessUnivariateStatistic.getN()