de.lmu.ifi.dbs.elki.math.linearalgebra

Class Centroid

java.lang.Object

de.lmu.ifi.dbs.elki.math.linearalgebra.Centroid

All Implemented Interfaces:

FeatureVector<java.lang.Number>, NumberVector, SpatialComparable

Direct Known Subclasses:

ProjectedCentroid

public class Centroid
extends java.lang.Object
implements NumberVector

Class to compute the centroid of some data. This is a more numerically stable approach than simply taking the sum divided by the count.

Since:

0.4.0

Author:

Erich Schubert

Nested Class Summary

Nested classes/interfaces inherited from interface de.lmu.ifi.dbs.elki.data.NumberVector

NumberVector.Factory<V extends NumberVector>

Field Summary

Fields

Modifier and Type	Field and Description
protected double[]	elements Vector elements.
protected double	wsum The current weight.

Fields inherited from interface de.lmu.ifi.dbs.elki.data.NumberVector

ATTRIBUTE_SEPARATOR, FIELD, FIELD_1D, FIELD_2D, VARIABLE_LENGTH

Fields inherited from interface de.lmu.ifi.dbs.elki.data.FeatureVector

TYPE

Constructor Summary

Constructors

Constructor and Description
Centroid(int dim) Constructor.

Method Summary

Modifier and Type	Method and Description
double	doubleValue(int dimension) Returns the value in the specified dimension as double.
double[]	getArrayRef() Low-level access to the element array.
int	getDimensionality() The dimensionality of the vector space where of this FeatureVector of V is an element.
long	longValue(int dimension) Returns the value in the specified dimension as long.
static Centroid	make(Relation<? extends NumberVector> relation, DBIDs ids) Static constructor from an existing relation.
void	put(double[] val) Add a single value with weight 1.0.
void	put(double[] val, double weight) Add data with a given weight.
void	put(NumberVector val) Add a single value with weight 1.0.
void	put(NumberVector val, double weight) Add data with a given weight.
double[]	toArray() Returns a double array copy of this vector.

Methods inherited from class java.lang.Object

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

Methods inherited from interface de.lmu.ifi.dbs.elki.data.NumberVector

byteValue, floatValue, getMax, getMin, getValue, intValue, shortValue

Methods inherited from interface de.lmu.ifi.dbs.elki.data.FeatureVector

toString

Field Detail

wsum

protected double wsum

The current weight.

elements

protected double[] elements

Vector elements.

Constructor Detail

Centroid

public Centroid(int dim)

Constructor.

Parameters:

dim - Dimensionality

Method Detail

put

public void put(double[] val)

Add a single value with weight 1.0.

Parameters:

val - Value

put

public void put(double[] val,
                double weight)

Add data with a given weight.

Parameters:

val - data

weight - weight

put

public void put(NumberVector val)

Add a single value with weight 1.0.

Parameters:

val - Value

put

public void put(NumberVector val,
                double weight)

Add data with a given weight.

Parameters:

val - data

weight - weight

doubleValue

public double doubleValue(int dimension)

Description copied from interface: NumberVector

Returns the value in the specified dimension as double. Note: this might seem redundant with respect to getValue(dim).doubleValue(), but usually this is much more efficient due to boxing/unboxing cost.

Specified by:

doubleValue in interface NumberVector

Parameters:

dimension - the desired dimension, where 0 ≤ dimension < this.getDimensionality()

Returns:

the value in the specified dimension

longValue

public long longValue(int dimension)

Description copied from interface: NumberVector

Returns the value in the specified dimension as long. Note: this might seem redundant with respect to getValue(dim).longValue(), but usually this is much more efficient due to boxing/unboxing cost.

Specified by:

longValue in interface NumberVector

Parameters:

dimension - the desired dimension, where 0 ≤ dimension < this.getDimensionality()

Returns:

the value in the specified dimension

getDimensionality

public int getDimensionality()

Description copied from interface: FeatureVector

The dimensionality of the vector space where of this FeatureVector of V is an element.

Specified by:

getDimensionality in interface FeatureVector<java.lang.Number>

Specified by:

getDimensionality in interface SpatialComparable

Returns:

the number of dimensions of this FeatureVector of V

toArray

public double[] toArray()

Description copied from interface: NumberVector

Returns a double array copy of this vector.

Specified by:

toArray in interface NumberVector

Returns:

Copy as double[]

make

public static Centroid make(Relation<? extends NumberVector> relation,
                            DBIDs ids)

Static constructor from an existing relation.

Parameters:

relation - Relation to use

ids - IDs to use

Returns:

Centroid

getArrayRef

public double[] getArrayRef()

Low-level access to the element array.

Returns:

Array access