org.apache.mahout.common.distance
Class EuclideanDistanceMeasure

java.lang.Object
  extended by org.apache.mahout.common.distance.SquaredEuclideanDistanceMeasure
      extended by org.apache.mahout.common.distance.EuclideanDistanceMeasure
All Implemented Interfaces:
DistanceMeasure, Parametered

public class EuclideanDistanceMeasure
extends SquaredEuclideanDistanceMeasure

This class implements a Euclidean distance metric by summing the square root of the squared differences between each coordinate.

If you don't care about the true distance and only need the values for comparison, then the base class, SquaredEuclideanDistanceMeasure, will be faster since it doesn't do the actual square root of the squared differences.


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
EuclideanDistanceMeasure()
           
 
Method Summary
 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
 
Methods inherited from class org.apache.mahout.common.distance.SquaredEuclideanDistanceMeasure
configure, createParameters, getParameters
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

EuclideanDistanceMeasure

public EuclideanDistanceMeasure()
Method Detail

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
Overrides:
distance in class SquaredEuclideanDistanceMeasure
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
Overrides:
distance in class SquaredEuclideanDistanceMeasure
Parameters:
centroidLengthSquare - Square of the length of centroid
centroid - Centroid vector


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