edu.stanford.math.plex4.utility

Class RandomUtility

java.lang.Object

edu.stanford.math.plex4.utility.RandomUtility

public class RandomUtility
extends java.lang.Object

This class contains static members for generating random numbers.

Author:

Andrew Tausz, Tim Harrington

Constructor Summary

Constructors

Constructor and Description
RandomUtility()

Method Summary

Methods

Modifier and Type	Method and Description
static void	initializeWithSeed(int seed) This function initializes the seeds of the random number generators to the specified values.
static int	nextBernoulli(double p) This function returns a sample of a Bernoulli random variable with parameter p.
static double	nextNormal() This function returns a normal random number.
static double	nextUniform() This function returns a uniform random number in the open interval (0, 1).
static int	nextUniformInt(int from, int to) Returns a uniformly distributed integer in the inclusive interval {from, ..., to}
static int	nextUniformIntExcluded(int from, int to, int exclusion) This function returns an integer uniformly distributed in the set {from, ..., to} \ {exclusion}.
static double[]	normalArray(int length) This function returns an array of normally distributed random numbers.
static double[]	normalArray(int length, boolean normalize) This function returns an array of normally distributed random numbers.
static double[][]	normalMatrix(int rows, int columns) This function returns a matrix containing normally distributed random numbers.
static int[]	permute(int[] values) This function computes a random permutation of the input array, and then applies the permutation.
static gnu.trove.TIntHashSet	randomSubset(int subsetSize, int selectionSetSize) This function computes a random subset of size subsetSize from the set {0, ..., selectionSetSize - 1}.
static double[]	uniformArray(int length) This function returns an array of uniformly distributed random numbers.
static double[][]	uniformMatrix(int rows, int columns) This function returns a matrix containing uniformly distributed random numbers.

Methods inherited from class java.lang.Object

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

Constructor Detail

RandomUtility

public RandomUtility()

Method Detail

initializeWithSeed

public static void initializeWithSeed(int seed)

This function initializes the seeds of the random number generators to the specified values.

Parameters:

seed - the seed to initialize with

nextBernoulli

public static int nextBernoulli(double p)

This function returns a sample of a Bernoulli random variable with parameter p.

Parameters:

p - The probability of returning 1

Returns:

a Bernoulli random variable with probability p

nextUniform

public static double nextUniform()

This function returns a uniform random number in the open interval (0, 1).

Returns:

a double containing a uniform random number in (0, 1)

nextNormal

public static double nextNormal()

This function returns a normal random number.

Returns:

a normally distributed random number

nextUniformInt

public static int nextUniformInt(int from,
                 int to)

Returns a uniformly distributed integer in the inclusive interval {from, ..., to}

Parameters:

from - the start integer

to - the end integer

Returns:

an integer uniformly distributed in {from, ..., to}

nextUniformIntExcluded

public static int nextUniformIntExcluded(int from,
                         int to,
                         int exclusion)

This function returns an integer uniformly distributed in the set {from, ..., to} \ {exclusion}.

Parameters:

from - the lowest member of the set

to - the highest member of the set

exclusion - the member to exclude

Returns:

an integer uniformly distributed in {from, ..., to} \ {exclusion}

normalArray

public static double[] normalArray(int length,
                   boolean normalize)

This function returns an array of normally distributed random numbers.

Parameters:

length - the length of the array to create

normalize - whether to normalize the vector or not

Returns:

an array containing normally distributed random numbers

uniformArray

public static double[] uniformArray(int length)

This function returns an array of uniformly distributed random numbers.

Parameters:

length - the length of the array to create

Returns:

an array containing uniformly distributed random numbers

normalArray

public static double[] normalArray(int length)

This function returns an array of normally distributed random numbers.

Parameters:

length - the length of the array to create

Returns:

an array containing normally distributed random numbers

uniformMatrix

public static double[][] uniformMatrix(int rows,
                       int columns)

This function returns a matrix containing uniformly distributed random numbers.

Parameters:

rows - the number of rows in the returned matrix

columns - the number of columns in the returned matrix

Returns:

a matrix containing uniformly distributed random numbers

normalMatrix

public static double[][] normalMatrix(int rows,
                      int columns)

This function returns a matrix containing normally distributed random numbers.

Parameters:

rows - the number of rows in the returned matrix

columns - the number of columns in the returned matrix

Returns:

a matrix containing normally distributed random numbers

permute

public static int[] permute(int[] values)

This function computes a random permutation of the input array, and then applies the permutation. It performs the permutation in-place.

Parameters:

values - the array of integers to permute

randomSubset

public static gnu.trove.TIntHashSet randomSubset(int subsetSize,
                                 int selectionSetSize)

This function computes a random subset of size subsetSize from the set {0, ..., selectionSetSize - 1}.

Parameters:

subsetSize - the size of the subset to return

selectionSetSize - the size of the set to select from

Returns:

a subset of size subsetSize from the set {0, ..., selectionSetSize - 1}