Package org.eclipse.jetty.util.statistic

Class SampleStatistic

java.lang.Object

org.eclipse.jetty.util.statistic.SampleStatistic

public class SampleStatistic
extends Object

Statistics on a sampled value.

Provides max, total, mean, count, variance, and standard deviation of continuous sequence of samples.

Calculates estimates of mean, variance, and standard deviation characteristics of a sample using a non synchronized approximation of the on-line algorithm presented in Donald Knuth's Art of Computer Programming, Volume 2, Semi numerical Algorithms, 3rd edition, page 232, Boston: Addison-Wesley. That cites a 1962 paper by B.P. Welford: Note on a Method for Calculating Corrected Sums of Squares and Products

This algorithm is also described in Wikipedia in the section "Online algorithm": Algorithms for calculating variance.

Constructor Summary

Constructors

Constructor	Description
SampleStatistic()

Method Summary

Modifier and Type	Method	Description
long	getCount()
long	getMax()
double	getMean()
double	getStdDev()
long	getTotal()
double	getVariance()
void	record(long sample)	Records a sample value.
void	reset()	Resets the statistics.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Details

SampleStatistic

public SampleStatistic()

Method Details

reset

public void reset()

Resets the statistics.

record

public void record(long sample)

Records a sample value.

Parameters:

sample - the value to record.

getMax

public long getMax()

Returns:

the max value of the recorded samples

getTotal

public long getTotal()

Returns:

the sum of all the recorded samples

getCount

public long getCount()

Returns:

the number of samples recorded

getMean

public double getMean()

Returns:

the average value of the samples recorded, or zero if there are no samples

getVariance

public double getVariance()

Returns:

the variance of the samples recorded, or zero if there are less than 2 samples

getStdDev

public double getStdDev()

Returns:

the standard deviation of the samples recorded

toString

public String toString()

Overrides:

toString in class Object