org.apache.mahout.cf.taste.impl.common

Class FullRunningAverageAndStdDev

java.lang.Object

org.apache.mahout.cf.taste.impl.common.FullRunningAverage

org.apache.mahout.cf.taste.impl.common.FullRunningAverageAndStdDev

All Implemented Interfaces:

Serializable, RunningAverage, RunningAverageAndStdDev

public final class FullRunningAverageAndStdDev
extends FullRunningAverage
implements RunningAverageAndStdDev

Extends FullRunningAverage to add a running standard deviation computation. Uses Welford's method, as described at http://www.johndcook.com/standard_deviation.html

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
FullRunningAverageAndStdDev()
FullRunningAverageAndStdDev(int count, double average, double mk, double sk)

Method Summary

Modifier and Type	Method and Description
void	addDatum(double datum)
void	changeDatum(double delta)
double	getMk()
double	getSk()
double	getStandardDeviation()
RunningAverageAndStdDev	inverse()
void	removeDatum(double datum)
String	toString()

Methods inherited from class org.apache.mahout.cf.taste.impl.common.FullRunningAverage

getAverage, getCount

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.mahout.cf.taste.impl.common.RunningAverage

getAverage, getCount

Constructor Detail

FullRunningAverageAndStdDev

public FullRunningAverageAndStdDev()

FullRunningAverageAndStdDev

public FullRunningAverageAndStdDev(int count,
                                   double average,
                                   double mk,
                                   double sk)

Method Detail

getMk

public double getMk()

getSk

public double getSk()

getStandardDeviation

public double getStandardDeviation()

Specified by:

getStandardDeviation in interface RunningAverageAndStdDev

Returns:

standard deviation of data

addDatum

public void addDatum(double datum)

Specified by:

addDatum in interface RunningAverage

Overrides:

addDatum in class FullRunningAverage

Parameters:

datum - new item to add to the running average

removeDatum

public void removeDatum(double datum)

Specified by:

removeDatum in interface RunningAverage

Overrides:

removeDatum in class FullRunningAverage

Parameters:

datum - item to remove to the running average

changeDatum

public void changeDatum(double delta)

Specified by:

changeDatum in interface RunningAverage

Overrides:

changeDatum in class FullRunningAverage

Parameters:

delta - amount by which to change a datum in the running average

Throws:

UnsupportedOperationException

inverse

public RunningAverageAndStdDev inverse()

Specified by:

inverse in interface RunningAverage

Specified by:

inverse in interface RunningAverageAndStdDev

Overrides:

inverse in class FullRunningAverage

Returns:

a (possibly immutable) object whose average is the negative of this object's

toString

public String toString()

Overrides:

toString in class FullRunningAverage