io.warp10.script.aggregator

Class VarianceWelford

java.lang.Object

io.warp10.script.NamedWarpScriptFunction

io.warp10.script.aggregator.VarianceWelford

All Implemented Interfaces:

WarpScriptAggregatorFunction, WarpScriptBucketizerFunction, WarpScriptMapperFunction, WarpScriptReducerFunction

public class VarianceWelford
extends NamedWarpScriptFunction
implements WarpScriptMapperFunction, WarpScriptReducerFunction, WarpScriptBucketizerFunction

Aggregator to compute the variance on a list of datapoints. This implements Welford's algorithm for numerical stability, see https://www.johndcook.com/blog/2008/09/26/comparing-three-methods-of-computing-standard-deviation/

Constructor Summary

Constructors

Constructor and Description
VarianceWelford(java.lang.String name, boolean useBessel, boolean forbidNulls)

Method Summary

Modifier and Type	Method and Description
java.lang.Object	apply(java.lang.Object[] args)
java.lang.String	toString()

Methods inherited from class io.warp10.script.NamedWarpScriptFunction

getName, refSnapshot, setName

Methods inherited from class java.lang.Object

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

Constructor Detail

VarianceWelford

public VarianceWelford(java.lang.String name,
                       boolean useBessel,
                       boolean forbidNulls)

Method Detail

apply

public java.lang.Object apply(java.lang.Object[] args)
                       throws WarpScriptException

Specified by:

apply in interface WarpScriptAggregatorFunction

Throws:

WarpScriptException

toString

public java.lang.String toString()

Overrides:

toString in class NamedWarpScriptFunction