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

All Methods
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