de.lmu.ifi.dbs.elki.database.relation

Class RelationUtil

java.lang.Object

de.lmu.ifi.dbs.elki.database.relation.RelationUtil

public final class RelationUtil
extends Object

Utility functions for handling database relation.

Author:

Erich Schubert

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	RelationUtil.AscendingByDoubleRelation Sort objects by a double relation
static class	RelationUtil.CollectionFromRelation<O> Collection view on a database that retrieves the objects when needed.
static class	RelationUtil.DescendingByDoubleRelation Sort objects by a double relation
static class	RelationUtil.RelationObjectIterator<O> Iterator class that retrieves the given objects from the database.

Constructor Summary

Constructors

Modifier	Constructor and Description
private	RelationUtil() Fake constructor: do not instantiate.

Method Summary

Modifier and Type	Method and Description
static <V extends FeatureVector<?>> VectorFieldTypeInformation<V>	assumeVectorField(Relation<V> relation) Get the vector field type information from a relation.
static double[][]	computeMinMax(Relation<? extends NumberVector> relation) Determines the minimum and maximum values in each dimension of all objects stored in the given database.
static int	dimensionality(Relation<? extends SpatialComparable> relation) Get the dimensionality of a database relation.
static <V extends SpatialComparable> String	getColumnLabel(Relation<? extends V> rel, int col) Get the column name or produce a generic label "Column XY".
static <V extends NumberVector> NumberVector.Factory<V>	getNumberVectorFactory(Relation<V> relation) Get the number vector factory of a database relation.
static double[][]	relationAsMatrix(Relation<? extends NumberVector> relation, ArrayDBIDs ids) Copy a relation into a double matrix.
static <V extends NumberVector,T extends NumberVector> Relation<V>	relationUglyVectorCast(Relation<T> database) An ugly vector type cast unavoidable in some situations due to Generics.
static double[]	variances(Relation<? extends NumberVector> database, NumberVector centroid, DBIDs ids) Determines the variances in each dimension of the specified objects stored in the given database.

Methods inherited from class java.lang.Object

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

Constructor Detail

RelationUtil

private RelationUtil()

Fake constructor: do not instantiate.

Method Detail

assumeVectorField

public static <V extends FeatureVector<?>> VectorFieldTypeInformation<V> assumeVectorField(Relation<V> relation)

Get the vector field type information from a relation.

Type Parameters:

V - Vector type

Parameters:

relation - relation

Returns:

Vector field type information

getNumberVectorFactory

public static <V extends NumberVector> NumberVector.Factory<V> getNumberVectorFactory(Relation<V> relation)

Get the number vector factory of a database relation.

Type Parameters:

V - Vector type

Parameters:

relation - relation

Returns:

Vector field type information

dimensionality

public static int dimensionality(Relation<? extends SpatialComparable> relation)

Get the dimensionality of a database relation.

Parameters:

relation - relation

Returns:

Database dimensionality

computeMinMax

public static double[][] computeMinMax(Relation<? extends NumberVector> relation)

Determines the minimum and maximum values in each dimension of all objects stored in the given database.

Parameters:

relation - the database storing the objects

Returns:

Minimum and Maximum vector for the hyperrectangle

variances

public static double[] variances(Relation<? extends NumberVector> database,
                                 NumberVector centroid,
                                 DBIDs ids)

Determines the variances in each dimension of the specified objects stored in the given database.

Parameters:

database - the database storing the objects

ids - the ids of the objects

centroid - the centroid or reference vector of the ids

Returns:

the variances in each dimension of the specified objects

relationAsMatrix

public static double[][] relationAsMatrix(Relation<? extends NumberVector> relation,
                                          ArrayDBIDs ids)

Copy a relation into a double matrix. This is not recommended unless you need to modify the data temporarily.

Parameters:

relation - Relation

ids - IDs, with well-defined order (i.e. array)

Returns:

Data matrix

getColumnLabel

public static <V extends SpatialComparable> String getColumnLabel(Relation<? extends V> rel,
                                                                  int col)

Get the column name or produce a generic label "Column XY".

Type Parameters:

V - Vector type

Parameters:

rel - Relation

col - Column

Returns:

Label

relationUglyVectorCast

public static <V extends NumberVector,T extends NumberVector> Relation<V> relationUglyVectorCast(Relation<T> database)

An ugly vector type cast unavoidable in some situations due to Generics.

Type Parameters:

V - Base vector type

T - Derived vector type (is actually V, too)

Parameters:

database - Database

Returns:

Database