org.eclipse.jetty.util.statistic
Class SampleStatistic

java.lang.Object
  org.eclipse.jetty.util.statistic.SampleStatistic

public class SampleStatistic
extends Object

SampledStatistics

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, Seminumerical Algorithms, 3rd edition, page 232, Boston: Addison-Wesley. that cites a 1962 paper by B.P. Welford that can be found by following the link http://www.jstor.org/pss/1266577

This algorithm is also described in Wikipedia at http://en.wikipedia.org/w/index.php?title=Algorithms_for_calculating_variance§ion=4#On-line_algorithm

Field Summary

protected AtomicLong	_count
protected AtomicLong	_max
protected AtomicLong	_total
protected AtomicLong	_totalVariance100

Constructor Summary

SampleStatistic()

Method Summary

long	getCount()
long	getMax()
double	getMean()
double	getStdDev()
long	getTotal()
double	getVariance()
void	reset()
void	set(long sample)

Methods inherited from class java.lang.Object

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

Field Detail

_max

protected final AtomicLong _max

_total

protected final AtomicLong _total

_count

protected final AtomicLong _count

_totalVariance100

protected final AtomicLong _totalVariance100

Constructor Detail

SampleStatistic

public SampleStatistic()

Method Detail

reset

public void reset()

set

public void set(long sample)

getMax

public long getMax()

Returns:

the max value

getTotal

public long getTotal()

getCount

public long getCount()

getMean

public double getMean()

getVariance

public double getVariance()

getStdDev

public double getStdDev()