org.apache.mahout.math

Class ConstantVector

java.lang.Object

org.apache.mahout.math.AbstractVector

org.apache.mahout.math.ConstantVector

All Implemented Interfaces:

Cloneable, Vector

public class ConstantVector
extends AbstractVector

Implements a vector with all the same values.

Nested Class Summary

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

lengthSquared

Constructor Summary

Constructors

Constructor and Description
ConstantVector(double value, int size)

Method Summary

Methods

Modifier and Type	Method and Description
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	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
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
Vector	like() Return an empty vector of the same underlying class as the receiver
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

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

aggregate, aggregate, all, asFormatString, assign, assign, assign, assign, assign, assign, clone, createOptimizedCopy, cross, divide, dot, dotSelf, equals, get, getDistanceSquared, getElement, getLengthSquared, 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, viewPart, zSum

Methods inherited from class java.lang.Object

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

Constructor Detail

ConstantVector

public ConstantVector(double value,
              int size)

Method Detail

matrixLike

protected Matrix matrixLike(int rows,
                int columns)

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

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.

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 iterator() and iterateNonZero() return elements in ascending order by index.

iterator

public 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

Specified by:

iterator in class AbstractVector

Returns:

An Iterator over all elements

iterateNonZero

public Iterator<Vector.Element> iterateNonZero()

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

getQuick

public double getQuick(int index)

Return the value at the given index, without checking bounds

Parameters:

index - an int index

Returns:

the double at the index

like

public Vector like()

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

Returns:

a Vector

setQuick

public void setQuick(int index,
            double value)

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()

Return the number of values in the recipient

Returns:

an int

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.