Class OzaBagAdwin
- java.lang.Object
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- moa.AbstractMOAObject
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- moa.options.AbstractOptionHandler
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- moa.classifiers.AbstractClassifier
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- moa.classifiers.meta.OzaBagAdwin
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- All Implemented Interfaces:
Configurable
,Serializable
,CapabilitiesHandler
,Classifier
,MultiClassClassifier
,AWTRenderable
,Learner<Example<Instance>>
,MOAObject
,OptionHandler
- Direct Known Subclasses:
OzaBagAdwinML
public class OzaBagAdwin extends AbstractClassifier implements MultiClassClassifier, CapabilitiesHandler
Bagging for evolving data streams using ADWIN.ADWIN is a change detector and estimator that solves in a well-specified way the problem of tracking the average of a stream of bits or real-valued numbers. ADWIN keeps a variable-length window of recently seen items, with the property that the window has the maximal length statistically consistent with the hypothesis “there has been no change in the average value inside the window”.
More precisely, an older fragment of the window is dropped if and only if there is enough evidence that its average value differs from that of the rest of the window. This has two consequences: one, that change reliably declared whenever the window shrinks; and two, that at any time the average over the existing window can be reliably taken as an estimation of the current average in the stream (barring a very small or very recent change that is still not statistically visible). A formal and quantitative statement of these two points (a theorem) appears inAlbert Bifet and Ricard Gavaldà. Learning from time-changing data with adaptive windowing. In SIAM International Conference on Data Mining, 2007.
ADWIN is parameter- and assumption-free in the sense that it automatically detects and adapts to the current rate of change. Its only parameter is a confidence bound δ, indicating how confident we want to be in the algorithm’s output, inherent to all algorithms dealing with random processes. Also important, ADWIN does not maintain the window explicitly, but compresses it using a variant of the exponential histogram technique. This means that it keeps a window of length W using only O(log W) memory and O(log W) processing time per item.
ADWIN Bagging is the online bagging method of Oza and Rusell with the addition of the ADWIN algorithm as a change detector and as an estimator for the weights of the boosting method. When a change is detected, the worst classifier of the ensemble of classifiers is removed and a new classifier is added to the ensemble.See details in:
[BHPKG] Albert Bifet, Geoff Holmes, Bernhard Pfahringer, Richard Kirkby, and Ricard Gavaldà . New ensemble methods for evolving data streams. In 15th ACM SIGKDD International Conference on Knowledge Discovery and Data Mining, 2009.Example:
OzaBagAdwin -l HoeffdingTreeNBAdaptive -s 10
Parameters:
- -l : Classifier to train
- -s : The number of models in the bag
- Version:
- $Revision: 7 $
- Author:
- Albert Bifet (abifet at cs dot waikato dot ac dot nz)
- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description protected ADWIN[]
ADError
ClassOption
baseLearnerOption
protected Classifier[]
ensemble
IntOption
ensembleSizeOption
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Fields inherited from class moa.classifiers.AbstractClassifier
classifierRandom, modelContext, randomSeed, randomSeedOption, trainingWeightSeenByModel
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Fields inherited from class moa.options.AbstractOptionHandler
config
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Constructor Summary
Constructors Constructor Description OzaBagAdwin()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description ImmutableCapabilities
defineImmutableCapabilities()
Defines the set of capabilities the object has.void
getModelDescription(StringBuilder out, int indent)
Returns a string representation of the model.protected Measurement[]
getModelMeasurementsImpl()
Gets the current measurements of this classifier.
The reason for ...Impl methods: ease programmer burden by not requiring them to remember calls to super in overridden methods.String
getPurposeString()
Dictionary with option texts and objectsClassifier[]
getSubClassifiers()
Gets the classifiers of this ensemble.double[]
getVotesForInstance(Instance inst)
Predicts the class memberships for a given instance.boolean
isRandomizable()
Gets whether this learner needs a random seed.void
resetLearningImpl()
Resets this classifier.void
trainOnInstanceImpl(Instance inst)
Trains this classifier incrementally using the given instance.
The reason for ...Impl methods: ease programmer burden by not requiring them to remember calls to super in overridden methods.-
Methods inherited from class moa.classifiers.AbstractClassifier
contextIsCompatible, copy, correctlyClassifies, getAttributeNameString, getAWTRenderer, getClassLabelString, getClassNameString, getDescription, getModel, getModelContext, getModelMeasurements, getNominalValueString, getPredictionForInstance, getPredictionForInstance, getSublearners, getVotesForInstance, modelAttIndexToInstanceAttIndex, modelAttIndexToInstanceAttIndex, prepareForUseImpl, resetLearning, setModelContext, setRandomSeed, trainingHasStarted, trainingWeightSeenByModel, trainOnInstance, trainOnInstance
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Methods inherited from class moa.options.AbstractOptionHandler
getCLICreationString, getOptions, getPreparedClassOption, prepareClassOptions, prepareForUse, prepareForUse
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Methods inherited from class moa.AbstractMOAObject
copy, measureByteSize, measureByteSize, toString
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
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Methods inherited from interface moa.capabilities.CapabilitiesHandler
getCapabilities
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Methods inherited from interface moa.MOAObject
measureByteSize
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Methods inherited from interface moa.options.OptionHandler
getCLICreationString, getOptions, prepareForUse, prepareForUse
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Field Detail
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baseLearnerOption
public ClassOption baseLearnerOption
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ensembleSizeOption
public IntOption ensembleSizeOption
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ensemble
protected Classifier[] ensemble
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ADError
protected ADWIN[] ADError
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Method Detail
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getPurposeString
public String getPurposeString()
Description copied from class:AbstractOptionHandler
Dictionary with option texts and objects- Specified by:
getPurposeString
in interfaceOptionHandler
- Overrides:
getPurposeString
in classAbstractClassifier
- Returns:
- the string with the purpose of this object
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resetLearningImpl
public void resetLearningImpl()
Description copied from class:AbstractClassifier
Resets this classifier. It must be similar to starting a new classifier from scratch.
The reason for ...Impl methods: ease programmer burden by not requiring them to remember calls to super in overridden methods. Note that this will produce compiler errors if not overridden.- Specified by:
resetLearningImpl
in classAbstractClassifier
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trainOnInstanceImpl
public void trainOnInstanceImpl(Instance inst)
Description copied from class:AbstractClassifier
Trains this classifier incrementally using the given instance.
The reason for ...Impl methods: ease programmer burden by not requiring them to remember calls to super in overridden methods. Note that this will produce compiler errors if not overridden.- Specified by:
trainOnInstanceImpl
in classAbstractClassifier
- Parameters:
inst
- the instance to be used for training
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getVotesForInstance
public double[] getVotesForInstance(Instance inst)
Description copied from interface:Classifier
Predicts the class memberships for a given instance. If an instance is unclassified, the returned array elements must be all zero.- Specified by:
getVotesForInstance
in interfaceClassifier
- Specified by:
getVotesForInstance
in classAbstractClassifier
- Parameters:
inst
- the instance to be classified- Returns:
- an array containing the estimated membership probabilities of the test instance in each class
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isRandomizable
public boolean isRandomizable()
Description copied from interface:Learner
Gets whether this learner needs a random seed. Examples of methods that needs a random seed are bagging and boosting.- Specified by:
isRandomizable
in interfaceLearner<Example<Instance>>
- Returns:
- true if the learner needs a random seed.
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getModelDescription
public void getModelDescription(StringBuilder out, int indent)
Description copied from class:AbstractClassifier
Returns a string representation of the model.- Specified by:
getModelDescription
in classAbstractClassifier
- Parameters:
out
- the stringbuilder to add the descriptionindent
- the number of characters to indent
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getModelMeasurementsImpl
protected Measurement[] getModelMeasurementsImpl()
Description copied from class:AbstractClassifier
Gets the current measurements of this classifier.
The reason for ...Impl methods: ease programmer burden by not requiring them to remember calls to super in overridden methods. Note that this will produce compiler errors if not overridden.- Specified by:
getModelMeasurementsImpl
in classAbstractClassifier
- Returns:
- an array of measurements to be used in evaluation tasks
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getSubClassifiers
public Classifier[] getSubClassifiers()
Description copied from interface:Classifier
Gets the classifiers of this ensemble. Returns null if this learner is a single learner.- Specified by:
getSubClassifiers
in interfaceClassifier
- Overrides:
getSubClassifiers
in classAbstractClassifier
- Returns:
- an array of the learners of the ensemble
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defineImmutableCapabilities
public ImmutableCapabilities defineImmutableCapabilities()
Description copied from interface:CapabilitiesHandler
Defines the set of capabilities the object has. Should be overridden if the object's capabilities do not change.- Specified by:
defineImmutableCapabilities
in interfaceCapabilitiesHandler
- Overrides:
defineImmutableCapabilities
in classAbstractClassifier
- Returns:
- The capabilities of the object.
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