org.apache.mahout.common.distance

Class SquaredEuclideanDistanceMeasure

java.lang.Object

org.apache.mahout.common.distance.SquaredEuclideanDistanceMeasure

All Implemented Interfaces:

DistanceMeasure, Parametered

Direct Known Subclasses:

EuclideanDistanceMeasure

public class SquaredEuclideanDistanceMeasure
extends Object
implements DistanceMeasure

Like EuclideanDistanceMeasure but it does not take the square root.

Thus, it is not actually the Euclidean Distance, but it is saves on computation when you only need the distance for comparison and don't care about the actual value as a distance.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.mahout.common.parameters.Parametered

Parametered.ParameteredGeneralizations

Field Summary

Fields inherited from interface org.apache.mahout.common.parameters.Parametered

log

Constructor Summary

Constructors

Constructor and Description
SquaredEuclideanDistanceMeasure()

Method Summary

Modifier and Type	Method and Description
void	configure(org.apache.hadoop.conf.Configuration job)
void	createParameters(String prefix, org.apache.hadoop.conf.Configuration jobConf) EXPERT: consumers should never have to call this method.
double	distance(double centroidLengthSquare, Vector centroid, Vector v) Optimized version of distance metric for sparse vectors.
double	distance(Vector v1, Vector v2) Returns the distance metric applied to the arguments
Collection<Parameter<?>>	getParameters()

Methods inherited from class java.lang.Object

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

Constructor Detail

SquaredEuclideanDistanceMeasure

public SquaredEuclideanDistanceMeasure()

Method Detail

configure

public void configure(org.apache.hadoop.conf.Configuration job)

Specified by:

configure in interface Parametered

getParameters

public Collection<Parameter<?>> getParameters()

Specified by:

getParameters in interface Parametered

createParameters

public void createParameters(String prefix,
                             org.apache.hadoop.conf.Configuration jobConf)

Description copied from interface: Parametered

EXPERT: consumers should never have to call this method. It would be friendly visible to Parametered.ParameteredGeneralizations if java supported it. Calling this method should create a new list of parameters and is called

Specified by:

createParameters in interface Parametered

Parameters:

prefix - ends with a dot if not empty.

jobConf - configuration used for retrieving values

See Also:

invoking method, invoking method

distance

public double distance(Vector v1,
                       Vector v2)

Description copied from interface: DistanceMeasure

Returns the distance metric applied to the arguments

Specified by:

distance in interface DistanceMeasure

Parameters:

v1 - a Vector defining a multidimensional point in some feature space

v2 - a Vector defining a multidimensional point in some feature space

Returns:

a scalar doubles of the distance

distance

public double distance(double centroidLengthSquare,
                       Vector centroid,
                       Vector v)

Description copied from interface: DistanceMeasure

Optimized version of distance metric for sparse vectors. This distance computation requires operations proportional to the number of non-zero elements in the vector instead of the cardinality of the vector.

Specified by:

distance in interface DistanceMeasure

Parameters:

centroidLengthSquare - Square of the length of centroid

centroid - Centroid vector