Package org.anchoranalysis.math.statistics

Class VarianceCalculatorLong

Object

VarianceCalculatorLong

public class VarianceCalculatorLong
extends Object

Calculates variance efficiently, as successive values are added, using long to store sums internally.

This is similar to VarianceCalculatorDouble but is designed for int values rather than doubles.

Efficiency occurs by maintaining a running sum, sum-of-squares and count as values are added.

This is useful for calculating variance in sequential order in an online manner.

Author:

Owen Feehan

Constructor Summary

Constructors

Constructor	Description
VarianceCalculatorLong()
VarianceCalculatorLong(long sum, long sumSquares, long count)	Creates a new VarianceCalculatorLong instance.

Method Summary

Modifier and Type	Method	Description
void	add(int value)	Adds a value to the running sum.
void	add(int value, int instances)	Adds a multiple instances of a value to the running sum.
long	getCount()	The running count of values.
double	mean()	Calculate the mean, based on the current state of running-sums.
VarianceCalculatorLong	subtract(VarianceCalculatorLong toSubtract)	Subtracts the running-sums and count from another VarianceCalculatorLong from the current object's state.
double	variance()	Calculate the variance, based on the current state of running-sums.

Methods inherited from class java.lang.Object

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

Constructor Details

VarianceCalculatorLong

public VarianceCalculatorLong(long sum,
 long sumSquares,
 long count)

Creates a new VarianceCalculatorLong instance.

Parameters:

sum - The running sum of values.

sumSquares - The running sum of squares of values.

count - The running count of values.

VarianceCalculatorLong

public VarianceCalculatorLong()

Method Details

add

public void add(int value)

Adds a value to the running sum.

Parameters:

value - the value to add.

add

public void add(int value,
 int instances)

Adds a multiple instances of a value to the running sum.

Parameters:

value - the value to add.

instances - how many instances of value to add.

subtract

public VarianceCalculatorLong subtract(VarianceCalculatorLong toSubtract)

Subtracts the running-sums and count from another VarianceCalculatorLong from the current object's state.

This occurs immutably, and the currently object's state is unaffected.

Parameters:

toSubtract - the other VarianceCalculatorLong whose state is subtracted.

Returns:

a newly created VarianceCalculatorLong whose state is the current object minus toSubtract.

mean

public double mean()

Calculate the mean, based on the current state of running-sums.

Returns:

the mean.

variance

public double variance()

Calculate the variance, based on the current state of running-sums.

Returns:

the variance.

getCount

public long getCount()

The running count of values.