Package elki.distance
Class ArcCosineUnitlengthDistance
- java.lang.Object
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- elki.distance.ArcCosineUnitlengthDistance
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- All Implemented Interfaces:
Distance<NumberVector>
,NumberVectorDistance<NumberVector>
,PrimitiveDistance<NumberVector>
,SpatialPrimitiveDistance<NumberVector>
public class ArcCosineUnitlengthDistance extends java.lang.Object implements SpatialPrimitiveDistance<NumberVector>, NumberVectorDistance<NumberVector>
Arcus cosine distance function for feature vectors.The arc cosine distance is computed as the arcus from the cosine similarity value, i.e.,
arccos(<v1,v2>)
.Cosine similarity is defined as \[ \tfrac{\vec{x}\cdot\vec{y}}{||a||\cdot||b||} =_{||a||=||b||=1} \vec{x}\cdot\vec{y} \] Arcus cosine distance then is \[ \operatorname{arccos} \tfrac{\vec{x}\cdot\vec{y}}{||a||\cdot||b||} =_{||a||=||b||=1} \operatorname{arccos} \vec{x}\cdot\vec{y} \in [0;\pi] \]
This implementation assumes that \(||a||=||b||=1\). If this does not hold for your data, use
ArcCosineDistance
instead!CosineUnitlengthDistance
andSqrtCosineUnitlengthDistance
are a bit less expensive to compute, and will yield the same ranking of neighbors.- Since:
- 0.7.5
- Author:
- Erich Schubert
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
ArcCosineUnitlengthDistance.Par
Parameterization class.
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Field Summary
Fields Modifier and Type Field Description static ArcCosineUnitlengthDistance
STATIC
Static instance
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Constructor Summary
Constructors Constructor Description ArcCosineUnitlengthDistance()
Deprecated.Use static instance!
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Method Summary
All Methods Instance Methods Concrete 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()
double
minDist(SpatialComparable mbr1, SpatialComparable mbr2)
Computes the distance between the two given MBRs according to this distance function.java.lang.String
toString()
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Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
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Methods inherited from interface elki.distance.Distance
isMetric, isSquared, isSymmetric
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Methods inherited from interface elki.distance.SpatialPrimitiveDistance
instantiate
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Field Detail
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STATIC
public static final ArcCosineUnitlengthDistance STATIC
Static instance
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Constructor Detail
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ArcCosineUnitlengthDistance
@Deprecated public ArcCosineUnitlengthDistance()
Deprecated.Use static instance!Constructor - useSTATIC
instead.
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Method Detail
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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 interfaceNumberVectorDistance<NumberVector>
- Specified by:
distance
in interfacePrimitiveDistance<NumberVector>
- Parameters:
v1
- first DatabaseObjectv2
- second DatabaseObject- Returns:
- the distance between two given DatabaseObjects according to this distance function
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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 interfaceSpatialPrimitiveDistance<NumberVector>
- Parameters:
mbr1
- the first MBR objectmbr2
- the second MBR object- Returns:
- the distance between the two given MBRs according to this distance function
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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equals
public boolean equals(java.lang.Object obj)
- Overrides:
equals
in classjava.lang.Object
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hashCode
public int hashCode()
- Overrides:
hashCode
in classjava.lang.Object
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getInputTypeRestriction
public SimpleTypeInformation<? super NumberVector> getInputTypeRestriction()
Description copied from interface:Distance
Get the input data type of the function.- Specified by:
getInputTypeRestriction
in interfaceDistance<NumberVector>
- Specified by:
getInputTypeRestriction
in interfacePrimitiveDistance<NumberVector>
- Returns:
- Type restriction
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