cc.mallet.cluster
Class GreedyAgglomerative

java.lang.Object
  cc.mallet.cluster.Clusterer
      cc.mallet.cluster.KBestClusterer
          cc.mallet.cluster.HillClimbingClusterer
              cc.mallet.cluster.GreedyAgglomerative

All Implemented Interfaces:

java.io.Serializable

Direct Known Subclasses:

GreedyAgglomerativeByDensity

public class GreedyAgglomerative
extends HillClimbingClusterer

Greedily merges Instances until convergence. New merges are scored using NeighborEvaluator.

Since:

1.0

Version:

1.0

Author:

"Aron Culotta"

See Also:

HillClimbingClusterer, Serialized Form

Field Summary

protected boolean	converged True if should stop clustering.
protected PairwiseMatrix	scoreCache Cache for calls to NeighborhoodEvaluator.
protected double	stoppingThreshold Converged when merge score is below this value.

Fields inherited from class cc.mallet.cluster.HillClimbingClusterer

evaluator

Constructor Summary

GreedyAgglomerative(Pipe instancePipe, NeighborEvaluator evaluator, double stoppingThreshold)

Method Summary

boolean	converged(Clustering clustering)
protected double	getScore(Clustering clustering, int i, int j)
Clustering	improveClustering(Clustering clustering) For each pair of clusters, calculate the score of the Neighbor that would result from merging the two clusters.
Clustering	initializeClustering(InstanceList instances)
void	reset() Reset convergence to false so a new round of clustering can begin.
java.lang.String	toString()
protected void	updateScoreMatrix(Clustering clustering, int i, int j) Resets the values of clusters that have been merged.

Methods inherited from class cc.mallet.cluster.HillClimbingClusterer

cluster, cluster, clusterKBest, clusterKBest, getEvaluator

Methods inherited from class cc.mallet.cluster.Clusterer

getPipe

Methods inherited from class java.lang.Object

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

Field Detail

stoppingThreshold

protected double stoppingThreshold

Converged when merge score is below this value.

converged

protected boolean converged

True if should stop clustering.

scoreCache

protected PairwiseMatrix scoreCache

Cache for calls to NeighborhoodEvaluator. In some experiments, reduced running time by nearly half.

Constructor Detail

GreedyAgglomerative

public GreedyAgglomerative(Pipe instancePipe,
                           NeighborEvaluator evaluator,
                           double stoppingThreshold)

Parameters:

instancePipe - Pipe for each underying Instance.

evaluator - To score potential merges.

stoppingThreshold - Clustering converges when the evaluator score is below this value.

Method Detail

initializeClustering

public Clustering initializeClustering(InstanceList instances)

Specified by:

initializeClustering in class HillClimbingClusterer

Parameters:

instances -

Returns:

A singleton clustering (each Instance in its own cluster).

converged

public boolean converged(Clustering clustering)

Specified by:

converged in class HillClimbingClusterer

Returns:

True if clustering is complete.

reset

public void reset()

Reset convergence to false so a new round of clustering can begin.

Specified by:

reset in class HillClimbingClusterer

improveClustering

public Clustering improveClustering(Clustering clustering)

For each pair of clusters, calculate the score of the Neighbor that would result from merging the two clusters. Choose the merge that obtains the highest score. If no merge improves score, return original Clustering

Specified by:

improveClustering in class HillClimbingClusterer

Parameters:

clustering -

Returns:

getScore

protected double getScore(Clustering clustering,
                          int i,
                          int j)

Parameters:

clustering -

i -

j -

Returns:

The score for merging these two clusters.

updateScoreMatrix

protected void updateScoreMatrix(Clustering clustering,
                                 int i,
                                 int j)

Resets the values of clusters that have been merged.

Parameters:

clustering -

i -

j -

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object