Package elki.distance

Class CosineUnitlengthDistance

java.lang.Object

elki.distance.CosineUnitlengthDistance

All Implemented Interfaces:

Distance<NumberVector>, NumberVectorDistance<NumberVector>, PrimitiveDistance<NumberVector>, SpatialPrimitiveDistance<NumberVector>

Direct Known Subclasses:

SqrtCosineUnitlengthDistance

public class CosineUnitlengthDistance
extends java.lang.Object
implements SpatialPrimitiveDistance<NumberVector>, NumberVectorDistance<NumberVector>

Cosine distance function for unit length feature vectors.

The cosine distance is computed from the cosine similarity by 1-(cosine similarity).

Cosine similarity is defined as \[ \tfrac{\vec{x}\cdot\vec{y}}{||a||\cdot||b||} =_{||a||=||b||=1} \vec{x}\cdot\vec{y} \] Cosine distance then is defined as \[ 1 - \tfrac{\vec{x}\cdot\vec{y}}{||a||\cdot||b||} =_{||a||=||b||=1} 1-\vec{x}\cdot\vec{y} \in [0;2] \]

This implementation assumes that \(||a||=||b||=1\). If this does not hold for your data, use CosineDistance instead!

ArcCosineUnitlengthDistance or SqrtCosineUnitlengthDistance can be used if you need a metric, but are more expensive to computate.

Since:

0.7.5

Author:

Erich Schubert

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	CosineUnitlengthDistance.Par	Parameterization class.

Field Summary

Fields

Modifier and Type	Field	Description
static CosineUnitlengthDistance	STATIC	Static instance

Constructor Summary

Constructors

Constructor	Description
CosineUnitlengthDistance()	Deprecated. Use static instance

Method Summary

Modifier and Type	Method	Description
double	distance(NumberVector v1, NumberVector v2)	Computes the distance between two given DatabaseObjects according to this distance function.
boolean	equals(java.lang.Object obj)
SimpleTypeInformation<? super NumberVector>	getInputTypeRestriction()	Get the input data type of the function.
int	hashCode()
boolean	isSquared()	Squared distances, that would become metric after square root.
double	minDist(SpatialComparable mbr1, SpatialComparable mbr2)	Computes the distance between the two given MBRs according to this distance function.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Methods inherited from interface elki.distance.Distance

isMetric, isSymmetric

Methods inherited from interface elki.distance.SpatialPrimitiveDistance

instantiate

Field Detail

STATIC

public static final CosineUnitlengthDistance STATIC

Static instance

Constructor Detail

CosineUnitlengthDistance

@Deprecated
public CosineUnitlengthDistance()

Deprecated.

Use static instance

Constructor - use STATIC instead.

Method Detail

distance

public double distance(NumberVector v1,
                       NumberVector v2)

Description copied from interface: PrimitiveDistance

Computes the distance between two given DatabaseObjects according to this distance function.

Specified by:

distance in interface NumberVectorDistance<NumberVector>

Specified by:

distance in interface PrimitiveDistance<NumberVector>

Parameters:

v1 - first DatabaseObject

v2 - second DatabaseObject

Returns:

the distance between two given DatabaseObjects according to this distance function

minDist

public double minDist(SpatialComparable mbr1,
                      SpatialComparable mbr2)

Description copied from interface: SpatialPrimitiveDistance

Computes the distance between the two given MBRs according to this distance function.

Specified by:

minDist in interface SpatialPrimitiveDistance<NumberVector>

Parameters:

mbr1 - the first MBR object

mbr2 - the second MBR object

Returns:

the distance between the two given MBRs according to this distance function

isSquared

public boolean isSquared()

Description copied from interface: Distance

Squared distances, that would become metric after square root.

E.g. squared Euclidean.

Specified by:

isSquared in interface Distance<NumberVector>

Returns:

true when squared.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

getInputTypeRestriction

public SimpleTypeInformation<? super NumberVector> getInputTypeRestriction()

Description copied from interface: Distance

Get the input data type of the function.

Specified by:

getInputTypeRestriction in interface Distance<NumberVector>

Specified by:

getInputTypeRestriction in interface PrimitiveDistance<NumberVector>

Returns:

Type restriction