Feature Class Reference

#include <Feature.h>

Inheritance diagram for Feature:

List of all members.

Public Types
enum	FeatureType {   boolean, nominal, ordinal, numerical_discrete,   numerical_continuous }
Public Member Functions
virtual	~Feature ()
virtual FeatureType	getType () const =0
virtual const string	getName () const =0
virtual double	getPosition () const =0
bool	isExternalizable ()
virtual double	getDistance (Feature *f) const =0
virtual void	moveTowards (Feature *f, double factor)=0
virtual Feature *	clone () const =0
virtual string	serialize () const =0
virtual void	unserialize (string value)=0
virtual void	aggregate (aggregatelist samples)=0
virtual string	toString () const =0
Protected Member Functions
	Feature (bool ext)
	Feature ()
Protected Attributes
const bool	externalize

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Detailed Description

Feature interface

A feature represents a single dimension in the cluster space and implements the necessary funcionality to compare features of the same kind and measure distances between them. A feature is identified by a name which has to be unique in the scope of its feature provider. It abstracts the type and structure of the underlying sensor data and can also apply arbitrary data processing and transformation to the raw sensor data. Typically, a sensor (i.e. a FeatureProvider) will provide multiple features which are extracted using domain-specific knowledge.

A feature will also be referenced as sample. Samples are a more generic from of a feature only containing information about their position and without information about corresponding neighbours, age, error, etc.

See also:

FeatureProvider

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Member Enumeration Documentation

enum Feature::FeatureType

Possible feature types

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Constructor & Destructor Documentation

Feature::Feature (  bool  ext  )  [inline, protected]

Constructor for usage in PerstantFeature Sets the externalization flag to the given value. See also: extnlze

Feature::Feature (   )  [inline, protected]

Default constructor Sets the externalization flag to false. See also: extnlze

virtual Feature::~Feature (   )  [inline, virtual]

Destructor Empty virtual destructor to have an entry in the implementing classes method table. This ensures that derived classes get destructed correctly.

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Member Function Documentation

virtual void Feature::aggregate (  aggregatelist  samples  )  [pure virtual]

Aggregate a sample values from other sources Parameters: samples  A list of <timestamp, sample> tuples. Implemented in AbstractStringFeature, NumericalDiscreteFeature, NumericalContinuousFeature, PowerFeature, TimeFeature, and WlanActiveModeFeature.

virtual Feature* Feature::clone (   )  const [pure virtual]

Clone a feature A feature must be able to clone itself. This is typically implemented with a copy constructor, but should return a new object. Implemented in AbstractStringFeature, AbstractStringListFeature, NumericalDiscreteFeature, NumericalContinuousFeature, PowerFeature, TimeFeature, and WlanActiveModeFeature.

virtual double Feature::getDistance (  Feature *  f  )  const [pure virtual]

Calculates the distance between two features Parameters: f  Feature used for distance measurement. Returns: Distance between the two samples. The return value has to be in the interval [0; 1] to guarantee comparability among samples of different features. Implemented in AbstractStringFeature, AbstractStringListFeature, NumericalDiscreteFeature, NumericalContinuousFeature, PowerFeature, TimeFeature, and WlanActiveModeFeature.

virtual const string Feature::getName (   )  const [pure virtual]

Query a features name Returns: Name of the Feature in the format "Featureprovider.Feature" Implemented in AbstractStringFeature, AbstractStringListFeature, ActiveWindowFeature, AudioBandFeature, AudioMeanFeature, AudioPeakFeature, BluetoothPeersFeature, BluetoothNumPeersFeature, GSMCellFeature, NumericalDiscreteFeature, NumericalContinuousFeature, PowerFeature, SystemCommandStringListFeature, TimeFeature, WlanActiveEssidFeature, WlanActiveMacAddressFeature, WlanActiveModeFeature, WlanActiveSignalLevelFeature, WlanPeersFeature, and WlanNumPeersFeature.

virtual double Feature::getPosition (   )  const [pure virtual]

Query a features position Returns: The distance to the origin. Every implementation must take care that only values in the interval [0; 1] are returned. Remarks: This function is only for the purpose of internal search operations and visualisation and should not be used in any other context. Implemented in AbstractStringFeature, AbstractStringListFeature, NumericalDiscreteFeature, NumericalContinuousFeature, PowerFeature, TimeFeature, and WlanActiveModeFeature.

virtual FeatureType Feature::getType (   )  const [pure virtual]

Query a features type Returns: The type of the Feature. Implemented in AbstractStringFeature, NumericalDiscreteFeature, NumericalContinuousFeature, PowerFeature, TimeFeature, and WlanActiveModeFeature.

bool Feature::isExternalizable (   )  [inline]

Query externalization flag Returns: true if the feature is externalizeable ( i.e. it has persistend data that should be stored across restarts), false otherwise.

virtual void Feature::moveTowards (  Feature *  f, double  factor )  [pure virtual]

Move feature Moves the feature towards a given sample value by the specified factor (factor times the distance). If the factor is 0, the old feature value must not change. If the factor is 1, the new feature value should be equivalent to the sample s. Parameters: f  Feature used for distance measurement. factor  Distance weight. Implemented in AbstractStringFeature, AbstractStringListFeature, NumericalDiscreteFeature, NumericalContinuousFeature, PowerFeature, TimeFeature, and WlanActiveModeFeature.

virtual string Feature::serialize (   )  const [pure virtual]

Serialize a samples data to a string Returns: String representation of the samples data. Implemented in AbstractStringFeature, AbstractStringListFeature, NumericalDiscreteFeature, NumericalContinuousFeature, PowerFeature, TimeFeature, and WlanActiveModeFeature.

virtual string Feature::toString (   )  const [pure virtual]

This is only for testing. Implemented in AbstractStringFeature, AbstractStringListFeature, ActiveWindowFeature, AudioBandFeature, AudioMeanFeature, AudioPeakFeature, BluetoothPeersFeature, BluetoothNumPeersFeature, GSMCellFeature, NumericalDiscreteFeature, NumericalContinuousFeature, PowerFeature, SystemCommandStringListFeature, TimeFeature, WlanActiveEssidFeature, WlanActiveMacAddressFeature, WlanActiveModeFeature, WlanActiveSignalLevelFeature, WlanPeersFeature, and WlanNumPeersFeature.

virtual void Feature::unserialize (  string  value  )  [pure virtual]

Unserialize a samples data from a string Parameters: value  String representation of the samples data. Implemented in AbstractStringFeature, AbstractStringListFeature, NumericalDiscreteFeature, NumericalContinuousFeature, PowerFeature, TimeFeature, and WlanActiveModeFeature.

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Member Data Documentation

const bool Feature::externalize [protected]

Externalization flag If true, then this feature has persistent data which should be preserved across restarts of the application (e.g. a list of already seen feature values for nominal and ordinal types or maximum and minimum values for numerical types). For all persistant features, the object should be cast to PersistentFeature, because only subclasses of this type are (by policy) allowed to set this variable to true. See also: PersistantFeature

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The documentation for this class was generated from the following file:

• amw/src/cpp/cross/contextprediction/framework/Features/Feature.h

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