Package elki.clustering.silhouette

Class PAMSIL<O>

java.lang.Object

elki.clustering.kmedoids.PAM<O>

elki.clustering.silhouette.PAMSIL<O>

Type Parameters:

O - Input data type

All Implemented Interfaces:

Algorithm, ClusteringAlgorithm<Clustering<MedoidModel>>, KMedoidsClustering<O>

Direct Known Subclasses:

PAMMEDSIL

@Reference(authors="M. Van der Laan, K. Pollard, J. Bryan",title="A new partitioning around medoids algorithm",booktitle="Journal of Statistical Computation and Simulation 73(8)",url="https://doi.org/10.1080/0094965031000136012",bibkey="doi:10.1080/0094965031000136012") @Reference(authors="Lars Lenssen and Erich Schubert",title="Clustering by Direct Optimization of the Medoid Silhouette",booktitle="Int. Conf. on Similarity Search and Applications, SISAP 2022",url="https://doi.org/10.1007/978-3-031-17849-8_15",bibkey="DBLP:conf/sisap/LenssenS22")
public class PAMSIL<O>
extends PAM<O>

Clustering to optimize the Silhouette coefficient with a PAM-based swap heuristic. This is the baseline algorithm, but it is fairly expensive: each iteration it considers (n-k)k swaps, for each the Silhouette needs to be evaluated at n² cost. The overall complexity per iteration hence is O((n-k)k ((n-k)+n²)), i.e., O(n³) for small k, making this a quite expensive clustering method.

Reference:

M. Van der Laan, K. Pollard, J. Bryan
A new partitioning around medoids algorithm
Journal of Statistical Computation and Simulation 73(8)

This already incorporates some optimizations from:

Lars Lenssen and Erich Schubert
Clustering by Direct Optimization of the Medoid Silhouette
Int. Conf. on Similarity Search and Applications, SISAP 2022

Since:

0.8.0

Author:

Erich Schubert

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static class	PAMSIL.Instance	Instance for a single dataset.
static class	PAMSIL.Par<O>	Parameterization class.

Nested classes/interfaces inherited from interface elki.Algorithm

Algorithm.Utils

Field Summary

Fields

Modifier and Type	Field	Description
private static Logging	LOG	The logger for this class.

Fields inherited from class elki.clustering.kmedoids.PAM

distance, initializer, k, maxiter

Constructor Summary

Constructors

Constructor	Description
PAMSIL(Distance<? super O> distance, int k, int maxiter, KMedoidsInitialization<O> initializer)	Constructor.

Method Summary

Modifier and Type	Method	Description
protected Logging	getLogger()	Get the static class logger.
Clustering<MedoidModel>	run(Relation<O> relation, int k, DistanceQuery<? super O> distQ)	Run k-medoids clustering with a given distance query. Not a very elegant API, but needed for some types of nested k-medoids.

Methods inherited from class elki.clustering.kmedoids.PAM

getInputTypeRestriction, initialMedoids, run, wrapResult

Methods inherited from class java.lang.Object

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

Methods inherited from interface elki.clustering.ClusteringAlgorithm

autorun

Field Detail

LOG

private static final Logging LOG

The logger for this class.

Constructor Detail

PAMSIL

public PAMSIL(Distance<? super O> distance,
              int k,
              int maxiter,
              KMedoidsInitialization<O> initializer)

Constructor.

Parameters:

distance - distance function

k - k parameter

maxiter - Maxiter parameter

initializer - Function to generate the initial means

Method Detail

run

public Clustering<MedoidModel> run(Relation<O> relation,
                                   int k,
                                   DistanceQuery<? super O> distQ)

Description copied from interface: KMedoidsClustering

Run k-medoids clustering with a given distance query.
Not a very elegant API, but needed for some types of nested k-medoids.

Specified by:

run in interface KMedoidsClustering<O>

Overrides:

run in class PAM<O>

Parameters:

relation - relation to use

k - Number of clusters

distQ - Distance query to use

Returns:

result

getLogger

protected Logging getLogger()

Description copied from class: PAM

Get the static class logger.

Overrides:

getLogger in class PAM<O>