common
Class SparseVector

java.lang.Object
  common.ImplicitVector
      common.SparseVector

public class SparseVector
extends ImplicitVector

Simple implementation of a sparse vector, that is, a vector of doubles in which many elements are zero. Only the non-zero elements are stored explicitly. The class uses two arrays: one to hold the non-zero values, and one to hold their indices. The indices (and corresponding values) are kept in sorted order, so accessing an element by index takes time logarithmic in the number of non-zero entries.

Constructor Summary

SparseVector()
Creates a new vector with no non-zero entries.

Method Summary

double	get(int i) Returns the value at the given index.
int	ithExplicitIndex(int i) Returns the ith explicitly represented index in this vector.
double	ithExplicitValue(int i) Returns the value at the ith explicitly represented index.
static void	main(java.lang.String[] args) Test program.
int	numExplicit() Returns the number of explicitly represented entries in this vector.
void	set(int i, double value) Sets the value at the given index.
java.lang.String	toString()

Methods inherited from class common.ImplicitVector

dotProduct, dotProduct, maxExplicitIndex, sampleIndex, sum

Methods inherited from class java.lang.Object

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

Constructor Detail

SparseVector

public SparseVector()

Creates a new vector with no non-zero entries.

Method Detail

get

public double get(int i)

Description copied from class: ImplicitVector

Returns the value at the given index. This is zero if no value is explicitly stored for the given index.

Specified by:

get in class ImplicitVector

set

public void set(int i,
                double value)

Sets the value at the given index. The value is stored explicitly only if it is non-zero.

Specified by:

set in class ImplicitVector

numExplicit

public int numExplicit()

Description copied from class: ImplicitVector

Returns the number of explicitly represented entries in this vector.

Specified by:

numExplicit in class ImplicitVector

ithExplicitIndex

public int ithExplicitIndex(int i)

Description copied from class: ImplicitVector

Returns the ith explicitly represented index in this vector.

Specified by:

ithExplicitIndex in class ImplicitVector

ithExplicitValue

public double ithExplicitValue(int i)

Description copied from class: ImplicitVector

Returns the value at the ith explicitly represented index.

Specified by:

ithExplicitValue in class ImplicitVector

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

main

public static void main(java.lang.String[] args)

Test program.