jsat.linear.distancemetrics

Class CosineDistanceNormalized

java.lang.Object

jsat.linear.distancemetrics.CosineDistanceNormalized

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, DistanceMetric

public class CosineDistanceNormalized
extends java.lang.Object
implements DistanceMetric

This distance metric returns the same cosine distance as CosineDistance. This implementation assumes that all vectors being passed in for distance computations have already been L2 normalized. This means the distance computation can be done more efficiently, but the results will be incorrect if the inputs have not already been normalized.
The word Normalized is postfixed to the name to avoid confusion, as many might assume "Normalized-CosineDistance" would mean a cosine distance with some form of additional normalization.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
CosineDistanceNormalized()

Method Summary

Modifier and Type	Method and Description
CosineDistanceNormalized	clone()
double	dist(Vec a, Vec b) Computes the distance between 2 vectors.
boolean	isIndiscemible() Returns true if this distance metric obeys the rule that, for any x and y ∈ S d(x, y) = 0 if and only if x = y
boolean	isSubadditive() Returns true if this distance metric obeys the rule that, for any x, y, and z ∈ S d(x, z) ≤ d(x, y) + d(y, z)
boolean	isSymmetric() Returns true if this distance metric obeys the rule that, for any x, y, and z ∈ S d(x, y) = d(y, x)
double	metricBound() All metrics must return values greater than or equal to 0.
java.lang.String	toString() Returns a descriptive name of the Distance Metric in use

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface jsat.linear.distancemetrics.DistanceMetric

dist, dist, dist, getAccelerationCache, getAccelerationCache, getQueryInfo, isValidMetric, supportsAcceleration

Constructor Detail

CosineDistanceNormalized

public CosineDistanceNormalized()

Method Detail

dist

public double dist(Vec a,
                   Vec b)

Description copied from interface: DistanceMetric

Computes the distance between 2 vectors. The smaller the value, the closer, and there for, more similar, the vectors are. 0 indicates the vectors are the same.

Specified by:

dist in interface DistanceMetric

Parameters:

a - the first vector

b - the second vector

Returns:

the distance between them

isSymmetric

public boolean isSymmetric()

Description copied from interface: DistanceMetric

Returns true if this distance metric obeys the rule that, for any x, y, and z ∈ S
d(x, y) = d(y, x)

Specified by:

isSymmetric in interface DistanceMetric

Returns:

true if this distance metric is symmetric, false if it is not

isSubadditive

public boolean isSubadditive()

Description copied from interface: DistanceMetric

Returns true if this distance metric obeys the rule that, for any x, y, and z ∈ S
d(x, z) ≤ d(x, y) + d(y, z)

Specified by:

isSubadditive in interface DistanceMetric

Returns:

true if this distance metric supports the triangle inequality, false if it does not.

isIndiscemible

public boolean isIndiscemible()

Description copied from interface: DistanceMetric

Returns true if this distance metric obeys the rule that, for any x and y ∈ S
d(x, y) = 0 if and only if x = y

Specified by:

isIndiscemible in interface DistanceMetric

Returns:

true if this distance metric is indicemible, false otherwise.

metricBound

public double metricBound()

Description copied from interface: DistanceMetric

All metrics must return values greater than or equal to 0. The upper bound on the value returned is different for different metrics. This method returns the theoretical maximal value that could be returned by this distance metric. That means Double.POSITIVE_INFINITY is a valid return value.

Specified by:

metricBound in interface DistanceMetric

Returns:

the maximal distance for any two points in that could exist by this distance metric.

toString

public java.lang.String toString()

Description copied from interface: DistanceMetric

Returns a descriptive name of the Distance Metric in use

Specified by:

toString in interface DistanceMetric

Overrides:

toString in class java.lang.Object

Returns:

the name of this metric

clone

public CosineDistanceNormalized clone()

Specified by:

clone in interface DistanceMetric

Overrides:

clone in class java.lang.Object