org.apache.mahout.math

Class VectorView

java.lang.Object

org.apache.mahout.math.AbstractVector

org.apache.mahout.math.VectorView

All Implemented Interfaces:

Cloneable, Vector

public class VectorView
extends AbstractVector

Implements subset view of a Vector

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	VectorView.AllIterator
class	VectorView.NonZeroIterator

Nested classes/interfaces inherited from class org.apache.mahout.math.AbstractVector

AbstractVector.LocalElement

Nested classes/interfaces inherited from interface org.apache.mahout.math.Vector

Vector.Element

Field Summary

Fields

Modifier and Type	Field and Description
protected int	offset
protected Vector	vector

Fields inherited from class org.apache.mahout.math.AbstractVector

lengthSquared

Constructor Summary

Constructors

Constructor and Description
VectorView() For serialization purposes only
VectorView(Vector vector, int offset, int cardinality)

Method Summary

Methods

Modifier and Type	Method and Description
Vector	clone() Return a copy of the recipient
double	getDistanceSquared(Vector v) Get the square of the distance between this vector and the other vector.
double	getIteratorAdvanceCost() Gets an estimate of the cost (in number of operations) it takes to advance an iterator through the nonzero elements of this vector.
double	getLengthSquared() Return the sum of squares of all elements in the vector.
double	getLookupCost() Gets an estimate of the cost (in number of operations) it takes to lookup a random element in this vector.
int	getNumNondefaultElements() Return the number of values in the recipient which are not the default value.
double	getQuick(int index) Return the value at the given index, without checking bounds
boolean	isAddConstantTime() Return true iff adding a new (nonzero) element takes constant time for this vector.
boolean	isDense()
boolean	isSequentialAccess()
Iterator<Vector.Element>	iterateNonZero() Iterates over all non-zero elements.
Iterator<Vector.Element>	iterator() Iterates over all elements * NOTE: Implementations may choose to reuse the Element returned for performance reasons, so if you need a copy of it, you should call AbstractVector.getElement(int) for the given index
VectorView	like() Return an empty vector of the same underlying class as the receiver
Vector	like(int cardinality) Return a new empty vector of the same underlying class as the receiver with given cardinality
protected Matrix	matrixLike(int rows, int columns) Subclasses must override to return an appropriately sparse or dense result
void	mergeUpdates(OrderedIntDoubleMapping updates) Used internally by assign() to update multiple indices and values at once.
void	setQuick(int index, double value) Set the value at the given index, without checking bounds
Vector	viewPart(int offset, int length) Return a new vector containing the subset of the recipient

Methods inherited from class org.apache.mahout.math.AbstractVector

aggregate, aggregate, all, asFormatString, assign, assign, assign, assign, assign, assign, createOptimizedCopy, cross, divide, dot, dotSelf, equals, get, getElement, getNumNonZeroElements, hashCode, incrementQuick, invalidateCachedLength, logNormalize, logNormalize, logNormalize, maxValue, maxValueIndex, minus, minValue, minValueIndex, nonZeroes, norm, normalize, normalize, plus, plus, set, size, sparseVectorToString, times, times, toString, toString, zSum

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

vector

protected Vector vector

offset

protected int offset

Constructor Detail

VectorView

public VectorView()

For serialization purposes only

VectorView

public VectorView(Vector vector,
          int offset,
          int cardinality)

Method Detail

matrixLike

protected Matrix matrixLike(int rows,
                int columns)

Description copied from class: AbstractVector

Subclasses must override to return an appropriately sparse or dense result

Specified by:

matrixLike in class AbstractVector

Parameters:

rows - the row cardinality

columns - the column cardinality

Returns:

a Matrix

clone

public Vector clone()

Description copied from interface: Vector

Return a copy of the recipient

Specified by:

clone in interface Vector

Overrides:

clone in class AbstractVector

Returns:

a new Vector

isDense

public boolean isDense()

Returns:

true iff this implementation should be considered dense -- that it explicitly represents every value

isSequentialAccess

public boolean isSequentialAccess()

Returns:

true iff this implementation should be considered to be iterable in index order in an efficient way. In particular this implies that Vector.all() and Vector.nonZeroes() ()} return elements in ascending order by index.

like

public VectorView like()

Description copied from interface: Vector

Return an empty vector of the same underlying class as the receiver

Returns:

a Vector

like

public Vector like(int cardinality)

Description copied from interface: Vector

Return a new empty vector of the same underlying class as the receiver with given cardinality

Returns:

getQuick

public double getQuick(int index)

Description copied from interface: Vector

Return the value at the given index, without checking bounds

Parameters:

index - an int index

Returns:

the double at the index

setQuick

public void setQuick(int index,
            double value)

Description copied from interface: Vector

Set the value at the given index, without checking bounds

Parameters:

index - an int index into the receiver

value - a double value to set

getNumNondefaultElements

public int getNumNondefaultElements()

Description copied from interface: Vector

Return the number of values in the recipient which are not the default value. For instance, for a sparse vector, this would be the number of non-zero values.

Returns:

an int

viewPart

public Vector viewPart(int offset,
              int length)

Description copied from interface: Vector

Return a new vector containing the subset of the recipient

Specified by:

viewPart in interface Vector

Overrides:

viewPart in class AbstractVector

Parameters:

offset - an int offset into the receiver

length - the cardinality of the desired result

Returns:

a new Vector

iterateNonZero

public Iterator<Vector.Element> iterateNonZero()

Description copied from class: AbstractVector

Iterates over all non-zero elements.

NOTE: Implementations may choose to reuse the Element returned for performance reasons, so if you need a copy of it, you should call AbstractVector.getElement(int) for the given index

Specified by:

iterateNonZero in class AbstractVector

Returns:

An Iterator over all non-zero elements

iterator

public Iterator<Vector.Element> iterator()

Description copied from class: AbstractVector

Iterates over all elements

* NOTE: Implementations may choose to reuse the Element returned for performance reasons, so if you need a copy of it, you should call AbstractVector.getElement(int) for the given index

Specified by:

iterator in class AbstractVector

Returns:

An Iterator over all elements

getLengthSquared

public double getLengthSquared()

Description copied from interface: Vector

Return the sum of squares of all elements in the vector. Square root of this value is the length of the vector.

Specified by:

getLengthSquared in interface Vector

Overrides:

getLengthSquared in class AbstractVector

Returns:

The sum of the squares of all elements in the vector.

getDistanceSquared

public double getDistanceSquared(Vector v)

Description copied from interface: Vector

Get the square of the distance between this vector and the other vector.

Specified by:

getDistanceSquared in interface Vector

Overrides:

getDistanceSquared in class AbstractVector

getLookupCost

public double getLookupCost()

Description copied from interface: Vector

Gets an estimate of the cost (in number of operations) it takes to lookup a random element in this vector.

getIteratorAdvanceCost

public double getIteratorAdvanceCost()

Description copied from interface: Vector

Gets an estimate of the cost (in number of operations) it takes to advance an iterator through the nonzero elements of this vector.

isAddConstantTime

public boolean isAddConstantTime()

Description copied from interface: Vector

Return true iff adding a new (nonzero) element takes constant time for this vector.

mergeUpdates

public void mergeUpdates(OrderedIntDoubleMapping updates)

Used internally by assign() to update multiple indices and values at once. Only really useful for sparse vectors (especially SequentialAccessSparseVector).

If someone ever adds a new type of sparse vectors, this method must merge (index, value) pairs into the vector.

Parameters:

updates - a mapping of indices to values to merge in the vector.