org.arp.javautil.stat

Class UpdatingVarCalc

java.lang.Object

org.arp.javautil.stat.UpdatingVarCalc

public class UpdatingVarCalc
extends Object

A class for calculating the variance and standard deviation of a list of values. Algorithm is due to West (Comm. ACM, Sep-79, Volume 22, Number 9, pp. 532-5).

Author:

Andrew Post

Constructor Summary

Constructors

Constructor and Description
UpdatingVarCalc(double val) Creates new UpdatingVarCalc.

Method Summary

Modifier and Type	Method and Description
void	addValue(double val) Update the variance with a new value.
double	getStdDev() Return the standard deviation of the list of values specified to this object.
double	getSumSquaredDeviations() Return the sum squared of the list of values specified to this object.
double	getVariance() Return the variance of the list of values specified to this object.

Methods inherited from class java.lang.Object

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

Constructor Detail

UpdatingVarCalc

public UpdatingVarCalc(double val)

Creates new UpdatingVarCalc. At least one point must be specified in order to calculate the variance or standard deviation. The first point should be specified in this constructor.

Parameters:

val - the first of a list of points.

Method Detail

addValue

public void addValue(double val)

Update the variance with a new value.

Parameters:

val - a new value.

getSumSquaredDeviations

public double getSumSquaredDeviations()

Return the sum squared of the list of values specified to this object.

Returns:

the sum squared of the list of values specified to this object.

getVariance

public double getVariance()

Return the variance of the list of values specified to this object.

Returns:

the variance of the list of values specified to this object.

getStdDev

public double getStdDev()

Return the standard deviation of the list of values specified to this object.

Returns:

the standard deviation of the list of values specified to this object.