de.lmu.ifi.dbs.elki.algorithm.outlier
Class ReferenceBasedOutlierDetection<V extends NumberVector<?,?>,D extends NumberDistance<D,?>>

java.lang.Object
  de.lmu.ifi.dbs.elki.algorithm.AbstractAlgorithm<OutlierResult>
      de.lmu.ifi.dbs.elki.algorithm.outlier.ReferenceBasedOutlierDetection<V,D>

Type Parameters:

V - a type of NumberVector as a suitable data object for this algorithm

D - the distance type processed

All Implemented Interfaces:

Algorithm, OutlierAlgorithm, InspectionUtilFrequentlyScanned, Parameterizable

@Title(value="An Efficient Reference-based Approach to Outlier Detection in Large Datasets")
@Description(value="Computes kNN distances approximately, using reference points with various reference point strategies.")
@Reference(authors="Y. Pei, O.R. Zaiane, Y. Gao",
           title="An Efficient Reference-based Approach to Outlier Detection in Large Datasets",
           booktitle="Proc. 19th IEEE Int. Conf. on Data Engineering (ICDE \'03), Bangalore, India, 2003",
           url="http://dx.doi.org/10.1109/ICDM.2006.17")
public class ReferenceBasedOutlierDetection<V extends NumberVector<?,?>,D extends NumberDistance<D,?>>
extends AbstractAlgorithm<OutlierResult>
implements OutlierAlgorithm

provides the Reference-Based Outlier Detection algorithm, an algorithm that computes kNN distances approximately, using reference points.

Reference:
Y. Pei, O. R. Zaiane, Y. Gao: An Efficient Reference-Based Approach to Outlier Detection in Large Datasets.
In: Proc. IEEE Int. Conf. on Data Mining (ICDM'06), Hong Kong, China, 2006.

Nested Class Summary

static class

ReferenceBasedOutlierDetection.Parameterizer<V extends NumberVector<?,?>,D extends NumberDistance<D,?>> Parameterization class.

Field Summary

private DistanceFunction<V,D>	distanceFunction Distance function to use.
private int	k Holds the value of K_ID.
static OptionID	K_ID Parameter to specify the number of nearest neighbors of an object, to be considered for computing its REFOD_SCORE, must be an integer greater than 1.
private static Logging	logger The logger for this class.
private ReferencePointsHeuristic<V>	refp Stores the reference point strategy
static OptionID	REFP_ID Parameter for the reference points heuristic.

Constructor Summary

ReferenceBasedOutlierDetection(int k, DistanceFunction<V,D> distanceFunction, ReferencePointsHeuristic<V> refp)
Constructor with parameters.

Method Summary

protected double	computeDensity(List<DistanceResultPair<D>> referenceDists, int index) Computes the density of an object.
protected List<DistanceResultPair<D>>	computeDistanceVector(V refPoint, Relation<V> database, DistanceQuery<V,D> distFunc) Computes for each object the distance to one reference point.
TypeInformation[]	getInputTypeRestriction() Get the input type restriction used for negotiating the data query.
protected Logging	getLogger() Get the (STATIC) logger for this class.
OutlierResult	run(Relation<V> relation) Run the algorithm on the given relation.

Methods inherited from class de.lmu.ifi.dbs.elki.algorithm.AbstractAlgorithm

makeParameterDistanceFunction, run

Methods inherited from class java.lang.Object

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

Methods inherited from interface de.lmu.ifi.dbs.elki.algorithm.outlier.OutlierAlgorithm

run

Field Detail

logger

private static final Logging logger

The logger for this class.

REFP_ID

public static final OptionID REFP_ID

Parameter for the reference points heuristic.

K_ID

public static final OptionID K_ID

Parameter to specify the number of nearest neighbors of an object, to be considered for computing its REFOD_SCORE, must be an integer greater than 1.

k

private int k

Holds the value of K_ID.

refp

private ReferencePointsHeuristic<V extends NumberVector<?,?>> refp

Stores the reference point strategy

distanceFunction

private DistanceFunction<V extends NumberVector<?,?>,D extends NumberDistance<D,?>> distanceFunction

Distance function to use.

Constructor Detail

ReferenceBasedOutlierDetection

public ReferenceBasedOutlierDetection(int k,
                                      DistanceFunction<V,D> distanceFunction,
                                      ReferencePointsHeuristic<V> refp)

Constructor with parameters.

Parameters:

k - k Parameter

distanceFunction - distance function

refp - Reference points heuristic

Method Detail

run

public OutlierResult run(Relation<V> relation)

Run the algorithm on the given relation.

Parameters:

relation - Relation to process

Returns:

Outlier result

computeDistanceVector

protected List<DistanceResultPair<D>> computeDistanceVector(V refPoint,
                                                            Relation<V> database,
                                                            DistanceQuery<V,D> distFunc)

Computes for each object the distance to one reference point. (one dimensional representation of the data set)

Parameters:

refPoint - Reference Point Feature Vector

database - database to work on

distFunc - Distance function to use

Returns:

array containing the distance to one reference point for each database object and the object id

computeDensity

protected double computeDensity(List<DistanceResultPair<D>> referenceDists,
                                int index)

Computes the density of an object. The density of an object is the distances to the k nearest neighbors. Neighbors and distances are computed approximately. (approximation for kNN distance: instead of a normal NN search the NN of an object are those objects that have a similar distance to a reference point. The k- nearest neighbors of an object are those objects that lay close to the object in the reference distance vector)

Parameters:

referenceDists - vector of the reference distances,

index - index of the current object

Returns:

density for one object and reference point

getInputTypeRestriction

public TypeInformation[] getInputTypeRestriction()

Description copied from class: AbstractAlgorithm

Get the input type restriction used for negotiating the data query.

Specified by:

getInputTypeRestriction in interface Algorithm

Specified by:

getInputTypeRestriction in class AbstractAlgorithm<OutlierResult>

Returns:

Type restriction

getLogger

protected Logging getLogger()

Description copied from class: AbstractAlgorithm

Get the (STATIC) logger for this class.

Specified by:

getLogger in class AbstractAlgorithm<OutlierResult>

Returns:

the static logger