net.sf.jagg
Class VarianceAggregator

java.lang.Object
  net.sf.jagg.Aggregator
      net.sf.jagg.AbstractVarianceAggregator
          net.sf.jagg.VarianceAggregator

public class VarianceAggregator
extends AbstractVarianceAggregator

This class represents the "sample variance" aggregator over numeric values.

Since:

0.1.0

Author:

Randy Gettman

Field Summary

Fields inherited from class net.sf.jagg.AbstractVarianceAggregator

myCount, mySum, myVarNumerator

Fields inherited from class net.sf.jagg.Aggregator

PROP_SELF

Constructor Summary

VarianceAggregator(java.lang.String property)
Constructs an VarianceAggregator that operates on the specified property.

Method Summary

VarianceAggregator	replicate() Returns an uninitialized copy of this Aggregator object, with the same property(ies) to analyze.
java.lang.Double	terminate() Return the sample variance by dividing the variance numerator by (n - 1), where n is the number of non-null pairs of numbers.
DoubleDouble	terminateDoubleDouble() Return the result as a DoubleDouble.

Methods inherited from class net.sf.jagg.AbstractVarianceAggregator

init, iterate, merge

Methods inherited from class net.sf.jagg.Aggregator

equals, getAggregator, getAggregator, getProperty, getValueFromProperty, hashCode, isInUse, setInUse, setProperty, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

VarianceAggregator

public VarianceAggregator(java.lang.String property)

Constructs an VarianceAggregator that operates on the specified property.

Parameters:

property - Calculate the variance of this property's values.

Method Detail

replicate

public VarianceAggregator replicate()

Returns an uninitialized copy of this Aggregator object, with the same property(ies) to analyze.

Specified by:

replicate in class Aggregator

Returns:

An uninitialized copy of this Aggregator object.

terminate

public java.lang.Double terminate()

Return the sample variance by dividing the variance numerator by (n - 1), where n is the number of non-null pairs of numbers.

Specified by:

terminate in class Aggregator

Returns:

The sample variance as a Double, NaN if no values have been accumulated, or 0 if exactly one value has been accumulated.

terminateDoubleDouble

public DoubleDouble terminateDoubleDouble()

Return the result as a DoubleDouble. This is used mainly when other Aggregators that use this result must maintain a high precision.

Specified by:

terminateDoubleDouble in class AbstractVarianceAggregator

Returns:

The sample variance as a DoubleDouble, NaN if no values have been accumulated, or 0 if exactly one value has been accumulated.

Since:

0.4.0

See Also:

DoubleDouble