de.lmu.ifi.dbs.elki.data

Class VectorUtil

java.lang.Object

de.lmu.ifi.dbs.elki.data.VectorUtil

public final class VectorUtil
extends java.lang.Object

Utility functions for use with vectors. Note: obviously, many functions are class methods or database related. TODO: add more precise but slower O(n^2) angle computation according to: Computing the Angle between Vectors, P. Schatte Journal of Computing, Volume 63, Number 1 (1999)

Since:

0.3

Author:

Erich Schubert

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	VectorUtil.SortDBIDsBySingleDimension Compare number vectors by a single dimension.
static class	VectorUtil.SortVectorsBySingleDimension Compare number vectors by a single dimension.

Constructor Summary

Constructors

Modifier	Constructor and Description
private	VectorUtil() Fake constructor.

Method Summary

Modifier and Type	Method and Description
static double	angle(NumberVector v1, NumberVector v2, NumberVector o) Compute the angle between two vectors with respect to a reference point.
static double	angleDense(NumberVector v1, NumberVector v2) Compute the absolute cosine of the angle between two dense vectors.
static double	angleSparse(SparseNumberVector v1, SparseNumberVector v2) Compute the angle for sparse vectors.
static double	angleSparseDense(SparseNumberVector v1, NumberVector v2) Compute the angle for a sparse and a dense vector.
static double	cosAngle(NumberVector v1, NumberVector v2) Compute the absolute cosine of the angle between two vectors.
static double	dot(NumberVector v1, NumberVector v2) Compute the dot product of the angle between two vectors.
static double	dotDense(NumberVector v1, NumberVector v2) Compute the dot product of two dense vectors.
static double	dotSparse(SparseNumberVector v1, SparseNumberVector v2) Compute the dot product for two sparse vectors.
static double	dotSparseDense(SparseNumberVector v1, NumberVector v2) Compute the dot product for a sparse and a dense vector.
static double	minCosAngle(SpatialComparable v1, SpatialComparable v2) Compute the minimum angle between two rectangles.
static double	minDot(SpatialComparable v1, SpatialComparable v2) Compute the minimum angle between two rectangles, assuming unit length vectors
static <V extends NumberVector> V	project(V v, long[] selectedAttributes, NumberVector.Factory<V> factory) Project a number vector to the specified attributes.
static <V extends NumberVector> V	randomVector(NumberVector.Factory<V> factory, int dim) Produce a new vector based on random numbers in [0:1].
static <V extends NumberVector> V	randomVector(NumberVector.Factory<V> factory, int dim, java.util.Random r) Produce a new vector based on random numbers in [0:1].

Methods inherited from class java.lang.Object

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

Constructor Detail

VectorUtil

private VectorUtil()

Fake constructor. Do not instantiate, use static methods.

Method Detail

randomVector

public static <V extends NumberVector> V randomVector(NumberVector.Factory<V> factory,
                                                      int dim,
                                                      java.util.Random r)

Produce a new vector based on random numbers in [0:1].

Type Parameters:

V - vector type

Parameters:

factory - Vector factory

dim - desired dimensionality

r - Random generator

Returns:

new instance

randomVector

public static <V extends NumberVector> V randomVector(NumberVector.Factory<V> factory,
                                                      int dim)

Produce a new vector based on random numbers in [0:1].

Type Parameters:

V - vector type

Parameters:

factory - Vector factory

dim - desired dimensionality

Returns:

new instance

angleDense

public static double angleDense(NumberVector v1,
                                NumberVector v2)

Compute the absolute cosine of the angle between two dense vectors. To convert it to radians, use Math.acos(angle)!

Parameters:

v1 - first vector

v2 - second vector

Returns:

Angle

angleSparse

public static double angleSparse(SparseNumberVector v1,
                                 SparseNumberVector v2)

Compute the angle for sparse vectors.

Parameters:

v1 - First vector

v2 - Second vector

Returns:

angle

angleSparseDense

public static double angleSparseDense(SparseNumberVector v1,
                                      NumberVector v2)

Compute the angle for a sparse and a dense vector.

Parameters:

v1 - Sparse first vector

v2 - Dense second vector

Returns:

angle

cosAngle

public static double cosAngle(NumberVector v1,
                              NumberVector v2)

Compute the absolute cosine of the angle between two vectors. To convert it to radians, use Math.acos(angle)!

Parameters:

v1 - first vector

v2 - second vector

Returns:

Angle

minCosAngle

public static double minCosAngle(SpatialComparable v1,
                                 SpatialComparable v2)

Compute the minimum angle between two rectangles.

Parameters:

v1 - first rectangle

v2 - second rectangle

Returns:

Angle

angle

public static double angle(NumberVector v1,
                           NumberVector v2,
                           NumberVector o)

Compute the angle between two vectors with respect to a reference point.

Parameters:

v1 - first vector

v2 - second vector

o - Origin

Returns:

Angle

dotDense

public static double dotDense(NumberVector v1,
                              NumberVector v2)

Compute the dot product of two dense vectors.

Parameters:

v1 - first vector

v2 - second vector

Returns:

dot product

dotSparse

public static double dotSparse(SparseNumberVector v1,
                               SparseNumberVector v2)

Compute the dot product for two sparse vectors.

Parameters:

v1 - First vector

v2 - Second vector

Returns:

dot product

dotSparseDense

public static double dotSparseDense(SparseNumberVector v1,
                                    NumberVector v2)

Compute the dot product for a sparse and a dense vector.

Parameters:

v1 - Sparse first vector

v2 - Dense second vector

Returns:

dot product

dot

public static double dot(NumberVector v1,
                         NumberVector v2)

Compute the dot product of the angle between two vectors.

Parameters:

v1 - first vector

v2 - second vector

Returns:

Dot product

minDot

public static double minDot(SpatialComparable v1,
                            SpatialComparable v2)

Compute the minimum angle between two rectangles, assuming unit length vectors

Parameters:

v1 - first rectangle

v2 - second rectangle

Returns:

Angle

project

public static <V extends NumberVector> V project(V v,
                                                 long[] selectedAttributes,
                                                 NumberVector.Factory<V> factory)

Project a number vector to the specified attributes.

Type Parameters:

V - Vector type

Parameters:

v - a NumberVector to project

selectedAttributes - the attributes selected for projection

factory - Vector factory

Returns:

a new NumberVector as a projection on the specified attributes