ch.akuhn.matrix

Class Vector

java.lang.Object

ch.akuhn.matrix.Vector

Direct Known Subclasses:

DenseVector, SparseVector

public abstract class Vector
extends Object

An ordered list of floating point numbers.

Author:

Adrian Kuhn

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	Vector.Entry An entry in a sparse vector

Constructor Summary

Constructors

Constructor and Description
Vector()

Method Summary

Modifier and Type	Method and Description
double	add(int index, double value) Add the given value to the value at the given index
void	applyCentering() mean-center the vector
static Vector	copy(double[] values, int start, int length) Copy a range from an array into a vector.
static Vector	dense(int size) Create an empty dense vector
double	density()
double	dot(Vector x) Returns the dot/scalar product.
Iterable<Vector.Entry>	entries() Iterates over all entries.
abstract boolean	equals(Vector v, double epsilon) Test for equality
static Vector	from(double... values) Construct a Vector from an array of values
abstract double	get(int index) Get the value at the given index
double	mean()
double	norm() Compute the L2 norm
abstract double	put(int index, double value) Set the value at an index
void	scaleAndAddTo(double a, Vector y) y = y + a*this.
abstract int	size()
static Vector	sparse(int size) Create an empty sparse vector
void	storeOn(double[] array, int start) I/O
double	sum()
abstract Vector	times(double scalar) Multiply by a constant, creating a new vector
abstract Vector	timesEquals(double scalar) Multiply by a constant in-place
String	toString()
double[]	unwrap()
int	used() Returns number of non-zero-valued entries.
static Vector	wrap(double... values) Wrap an array in a vector

Methods inherited from class java.lang.Object

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

Constructor Detail

Vector

public Vector()

Method Detail

add

public double add(int index,
                  double value)

Add the given value to the value at the given index

Parameters:

index -

value -

Returns:

the new value

density

public double density()

Returns:

the density

entries

public Iterable<Vector.Entry> entries()

Iterates over all entries. Some vectors omit zero-valued entries.

Returns:

value and index of each entry.

get

public abstract double get(int index)

Get the value at the given index

Parameters:

index -

Returns:

the value

norm

public double norm()

Compute the L2 norm

Returns:

the L2 norm

put

public abstract double put(int index,
                           double value)

Set the value at an index

Parameters:

index -

value -

Returns:

the new value

size

public abstract int size()

Returns:

the length of the vector

sum

public double sum()

Returns:

the sum of values

used

public int used()

Returns number of non-zero-valued entries.

Returns:

a positive integer.

from

public static Vector from(double... values)

Construct a Vector from an array of values

Parameters:

values -

Returns:

the vector

copy

public static Vector copy(double[] values,
                          int start,
                          int length)

Copy a range from an array into a vector.

Parameters:

values -

start -

length -

Returns:

the vector

wrap

public static Vector wrap(double... values)

Wrap an array in a vector

Parameters:

values -

Returns:

the vector

dense

public static Vector dense(int size)

Create an empty dense vector

Parameters:

size -

Returns:

the vector

sparse

public static Vector sparse(int size)

Create an empty sparse vector

Parameters:

size -

Returns:

the vector

dot

public double dot(Vector x)

Returns the dot/scalar product.

Parameters:

x -

Returns:

the dot product

scaleAndAddTo

public void scaleAndAddTo(double a,
                          Vector y)

y = y + a*this.

Parameters:

a -

y -

storeOn

public void storeOn(double[] array,
                    int start)

I/O

Parameters:

array -

start -

toString

public String toString()

Overrides:

toString in class Object

times

public abstract Vector times(double scalar)

Multiply by a constant, creating a new vector

Parameters:

scalar -

Returns:

the vector

timesEquals

public abstract Vector timesEquals(double scalar)

Multiply by a constant in-place

Parameters:

scalar -

Returns:

this

equals

public abstract boolean equals(Vector v,
                               double epsilon)

Test for equality

Parameters:

v -

epsilon -

Returns:

true if the same; false otherwise

unwrap

public double[] unwrap()

Returns:

an array

applyCentering

public void applyCentering()

mean-center the vector

mean

public double mean()

Returns:

the mean of the values