de.lmu.ifi.dbs.elki.math.linearalgebra.pca
Class SignificantEigenPairFilter

java.lang.Object
  de.lmu.ifi.dbs.elki.logging.AbstractLoggable
      de.lmu.ifi.dbs.elki.math.linearalgebra.pca.SignificantEigenPairFilter

All Implemented Interfaces:

EigenPairFilter, Parameterizable

@Title(value="Significant EigenPair Filter")
@Description(value="Sorts the eigenpairs in decending order of their eigenvalues and looks for the maxmimum contrast of current Eigenvalue / average of remaining Eigenvalues.")
public class SignificantEigenPairFilter
extends AbstractLoggable
implements EigenPairFilter, Parameterizable

The SignificantEigenPairFilter sorts the eigenpairs in descending order of their eigenvalues and chooses the contrast of an Eigenvalue to the remaining Eigenvalues is maximal. It is closely related to the WeakEigenPairFilter and RelativeEigenPairFilter. But while the RelativeEigenPairFilter chooses the highest dimensionality that satisfies the relative alpha levels, the SignificantEigenPairFilter will chose the local dimensionality such that the 'contrast' is maximal. There are some situations where one or the other is superior, especially when it comes to handling nested clusters and strong global correlations that are not too interesting. These benefits usually only make a difference at higher dimensionalities.

Author:

Erich Schubert

Field Summary

static double	DEFAULT_WALPHA The default value for walpha.
private double	walpha The noise tolerance level for weak eigenvectors
private DoubleParameter	WALPHA_PARAM Parameter weak alpha.

Fields inherited from class de.lmu.ifi.dbs.elki.logging.AbstractLoggable

debug, logger

Constructor Summary

SignificantEigenPairFilter(Parameterization config)
Constructor, adhering to Parameterizable

Method Summary

FilteredEigenPairs

filter(SortedEigenPairs eigenPairs) Filter eigenpairs

Methods inherited from class de.lmu.ifi.dbs.elki.logging.AbstractLoggable

debugFine, debugFiner, debugFinest, exception, progress, verbose, warning

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_WALPHA

public static final double DEFAULT_WALPHA

The default value for walpha. Not used by default, we're going for maximum contrast only.

See Also:

Constant Field Values

WALPHA_PARAM

private final DoubleParameter WALPHA_PARAM

Parameter weak alpha.

walpha

private double walpha

The noise tolerance level for weak eigenvectors

Constructor Detail

SignificantEigenPairFilter

public SignificantEigenPairFilter(Parameterization config)

Constructor, adhering to Parameterizable

Parameters:

config - Parameterization

Method Detail

filter

public FilteredEigenPairs filter(SortedEigenPairs eigenPairs)

Filter eigenpairs

Specified by:

filter in interface EigenPairFilter

Parameters:

eigenPairs - the eigenPairs (i.e. the eigenvectors and

Returns:

the filtered eigenpairs