net.librec.math.algorithm

Class Randoms

java.lang.Object

net.librec.math.algorithm.Randoms

public class Randoms
extends java.lang.Object

Author:

Guo Guibing

Constructor Summary

Constructors

Constructor and Description
Randoms()

Method Summary

Methods

Modifier and Type	Method and Description
static boolean	bernoulli() Return a boolean, which is true with probability .5, and false otherwise.
static boolean	bernoulli(double p) Return a boolean, which is true with probability p, and false otherwise.
static double	cauchy() Return a real number with a Cauchy distribution.
static void	clearCache()
static int	discrete(double[] a) Return a number from a discrete distribution: i with probability a[i].
static double[]	doubles(double min, double max, int size) A random double array with values in [min, max).
static double[]	doubles(int size) A random double array with values in [0, 1)
static double	exp(double lambda) Return a real number from an exponential distribution with rate lambda.
static double	gamma(double alpha, double scale) Randomly sample 1 point from Gamma Distribution with the given parameters.
static double	gaussian(double mu, double sigma) Return a real number from a Gaussian distribution with given mean and stddev.
static int[]	indexs(int size, int min, int max) Generate no repeat size indexes from min to max
static int[]	ints(int range, int size)
static int[]	ints(int min, int max, int size)
static java.util.List<java.lang.Double>	list(int size)
static java.util.List<java.lang.Double>	list(int size, int min, int max)
static java.util.List<java.lang.Double>	list(int size, int min, int max, boolean isInteger)
static int	nextInt(int range, int... exceptions) generate next random integer in a range besides exceptions
static int	nextInt(int min, int max, int... exceptions) generate next random integer in a range [min, max) besides exceptions
static int[]	nextIntArray(int length, int range) generate next integers array with no repeated elements
static int[]	nextIntArray(int length, int range, int... exceptions)
static int[]	nextIntArray(int length, int min, int max)
static int[]	nextIntArray(int length, int min, int max, int... exceptions)
static double	pareto(double alpha) Return a real number with a Pareto distribution with parameter alpha.
static java.util.List<java.lang.Integer>	permute(int min, int max) Generate a permutation from min to max
static int	poisson(double lambda) Return an integer with a Poisson distribution with mean lambda.
static java.util.List<java.lang.Integer>	randInts(int length, int min, int max) Generate a set of random (unique) integers in the range [min, max) with length length
static double	random() Return real number uniformly in [0, 1).
static <T> T	random(java.util.List<T> data) Return a random number from a given list of numbers.
static double[]	randProbs(int size) Get a normalize array of probabilities
static void	seed(long seed)
static double	uniform() Random (uniformly distributed) double in [0, 1)
static double	uniform(double min, double max) Random (uniformly distributed) double in [min, max)
static int	uniform(int range) Random generate an integer in [0, range)
static int	uniform(int min, int max) Random generate an integer in [min, max)
static DenseMatrix	wishart(DenseMatrix scale, double df) Randomly sample a matrix from Wishart Distribution with the given parameters.

Methods inherited from class java.lang.Object

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

Constructor Detail

Randoms

public Randoms()

Method Detail

uniform

public static int uniform(int range)

Random generate an integer in [0, range)

Parameters:

range - range of the interval

Returns:

an integer random generated in [0, range)

seed

public static void seed(long seed)

uniform

public static int uniform(int min,
          int max)

Random generate an integer in [min, max)

Parameters:

min - minimum of the range

max - maximum of the range

Returns:

an integer random generated in [min, max)

random

public static double random()

Return real number uniformly in [0, 1).

Returns:

real number uniformly in [0, 1).

random

public static <T> T random(java.util.List<T> data)

Return a random number from a given list of numbers.

Type Parameters:

T - type parameter

Parameters:

data - a given list of numbers

Returns:

a random number from a given list of numbers

doubles

public static double[] doubles(int size)

A random double array with values in [0, 1)

Parameters:

size - the size of random array

Returns:

a random double array with values in [0, 1)

doubles

public static double[] doubles(double min,
               double max,
               int size)

A random double array with values in [min, max).

Parameters:

min - minimum

max - maximum

size - the size of random array

Returns:

a random double array with values in [min, max)

uniform

public static double uniform()

Random (uniformly distributed) double in [0, 1)

Returns:

Random (uniformly distributed) double in [0, 1)

uniform

public static double uniform(double min,
             double max)

Random (uniformly distributed) double in [min, max)

Parameters:

max - max of the range

min - min of the range

Returns:

Random (uniformly distributed) double in [min, max)

bernoulli

public static boolean bernoulli(double p)

Return a boolean, which is true with probability p, and false otherwise.

Parameters:

p - probability p

Returns:

a boolean, which is true with probability p, and false otherwise.

bernoulli

public static boolean bernoulli()

Return a boolean, which is true with probability .5, and false otherwise.

Returns:

a boolean, which is true with probability .5, and false otherwise.

gaussian

public static double gaussian(double mu,
              double sigma)

Return a real number from a Gaussian distribution with given mean and stddev.

Parameters:

mu - mean

sigma - stddev

Returns:

a real number from a Gaussian distribution with given mean and stddev

gamma

public static double gamma(double alpha,
           double scale)

Randomly sample 1 point from Gamma Distribution with the given parameters. The code is from Mahout (http://mahout.apache.org/), available under Apache 2 license.

Parameters:

alpha - alpha parameter for Gamma Distribution.

scale - scale parameter for Gamma Distribution.

Returns:

a sample point randomly drawn from the given distribution.

wishart

public static DenseMatrix wishart(DenseMatrix scale,
                  double df)
                           throws LibrecException

Randomly sample a matrix from Wishart Distribution with the given parameters.

Parameters:

scale - scale parameter for Wishart Distribution.

df - degree of freedom for Wishart Distribution.

Returns:

the sample randomly drawn from the given distribution.

Throws:

LibrecException - if error occurs

poisson

public static int poisson(double lambda)

Return an integer with a Poisson distribution with mean lambda.

Parameters:

lambda - mean lambda

Returns:

an integer with a Poisson distribution with mean lambda

pareto

public static double pareto(double alpha)

Return a real number with a Pareto distribution with parameter alpha.

Parameters:

alpha - parameter alpha

Returns:

a real number with a Pareto distribution with parameter alpha.

cauchy

public static double cauchy()

Return a real number with a Cauchy distribution.

Returns:

a real number with a Cauchy distribution

discrete

public static int discrete(double[] a)

Return a number from a discrete distribution: i with probability a[i]. Precondition: array entries are nonnegative and their sum (very nearly) equals 1.0.

Parameters:

a - probability a[i]

Returns:

a number from the discrete distribution

exp

public static double exp(double lambda)

Return a real number from an exponential distribution with rate lambda.

Parameters:

lambda - rate lambda

Returns:

a real number from an exponential distribution with rate lambda.

nextInt

public static int nextInt(int range,
          int... exceptions)

generate next random integer in a range besides exceptions

Parameters:

range - the range located of next integer

exceptions - the exception values when generating integers, sorted first

Returns:

next no-repeated random integer

nextInt

public static int nextInt(int min,
          int max,
          int... exceptions)

generate next random integer in a range [min, max) besides exceptions

Parameters:

min - the minimum of range

max - the maximum of range

exceptions - the exception values when generating integers, sorted first

Returns:

next no-repeated random integer

indexs

public static int[] indexs(int size,
           int min,
           int max)

Generate no repeat size indexes from min to max

Parameters:

min - min of the range

max - max of the range

size - size of the index array

Returns:

no repeat size indexes from min to max

clearCache

public static void clearCache()

nextIntArray

public static int[] nextIntArray(int length,
                 int range)
                          throws java.lang.Exception

generate next integers array with no repeated elements

Parameters:

length - the length of the array

range - the index range of the array, default [0, range)

Returns:

ascending sorted integer array

Throws:

java.lang.Exception - if the range is less than length, an exception will be thrown

nextIntArray

public static int[] nextIntArray(int length,
                 int range,
                 int... exceptions)
                          throws java.lang.Exception

Throws:

java.lang.Exception

nextIntArray

public static int[] nextIntArray(int length,
                 int min,
                 int max)
                          throws java.lang.Exception

Throws:

java.lang.Exception

nextIntArray

public static int[] nextIntArray(int length,
                 int min,
                 int max,
                 int... exceptions)
                          throws java.lang.Exception

Throws:

java.lang.Exception

randInts

public static java.util.List<java.lang.Integer> randInts(int length,
                                         int min,
                                         int max)
                                                  throws java.lang.Exception

Generate a set of random (unique) integers in the range [min, max) with length length

Parameters:

max - max of the range

min - min of the range

length - length of the List

Returns:

a set of unique integers

Throws:

java.lang.Exception - if error occurs

randProbs

public static double[] randProbs(int size)

Get a normalize array of probabilities

Parameters:

size - array size

Returns:

a normalize array of probabilities

ints

public static int[] ints(int range,
         int size)

ints

public static int[] ints(int min,
         int max,
         int size)

list

public static java.util.List<java.lang.Double> list(int size)

list

public static java.util.List<java.lang.Double> list(int size,
                                    int min,
                                    int max)

list

public static java.util.List<java.lang.Double> list(int size,
                                    int min,
                                    int max,
                                    boolean isInteger)

permute

public static java.util.List<java.lang.Integer> permute(int min,
                                        int max)

Generate a permutation from min to max

Parameters:

min - the minimum value

max - the maximum value

Returns:

a permutation