Package org.flag4j.rng

Class RandomArray

java.lang.Object

org.flag4j.rng.RandomArray

public final class RandomArray
extends Object

This class contains methods useful for generating arrays filled with random values.

Field Summary

Fields

Modifier and Type	Field	Description
private final RandomCNumber	rng	Random number generator to use when creating random arrays.

Constructor Summary

Constructors

Constructor	Description
RandomArray()	Creates a RandomArray object to generate arrays filled with random values using a default random number generator.
RandomArray(RandomCNumber rng)	Creates a RandomArray object to generate arrays filled with random values using the specified complex random number generator.

Method Summary

Modifier and Type	Method	Description
CNumber[]	genNormalComplexArray(int length)	Generates an array of complex numbers with pseudorandom normally distributed magnitudes with a mean of 0.0 and a magnitude of 1.0.
CNumber[]	genNormalComplexArray(int length, double mean, double std)	Generates an array of complex numbers with pseudorandom normally distributed magnitudes with specified mean and standard deviation.
double[]	genNormalRealArray(int length)	Generates an array of doubles filled with normally pseudorandom values with a mean of 0 and standard deviation of 1.
double[]	genNormalRealArray(int length, double mean, double std)	Generates an array of doubles filled with normally distributed pseudorandom values with a specified mean and standard deviation.
private int[]	genRandomRows(int numIndices, int rowStart, int rowEnd, int maxReps)	Helper function to generate random row indices for use in randomUniqueIndices2D(int, int, int, int, int).
CNumber[]	genUniformComplexArray(int length)	Generates an array of complex numbers with pseudorandom uniformly distributed magnitudes in [0.0, 1.0).
CNumber[]	genUniformComplexArray(int length, double min, double max)	Generates an array of pseudorandom complex numbers with uniformly distributed magnitudes in [min, max).
double[]	genUniformRealArray(int length)	Generates an array of doubles filled with uniformly distributed pseudorandom values in [0.0, 1.0).
double[]	genUniformRealArray(int length, double min, double max)	Generates an array of doubles filled with uniformly distributed pseudorandom values in [min, max).
double[]	genUniformRealIntArray(int length)	Generates an array of integers filled with uniformly distributed pseudorandom int values in [Integer.MAX_VALUE, Integer.MAX_VALUE).
int[]	genUniformRealIntArray(int length, int min, int max)	Generates an array of integers filled with uniformly distributed pseudorandom values in [min, max).
int[]	randomUniqueIndices(int numIndices, int start, int end)	Creates unique indices in [start, end).
int[][]	randomUniqueIndices2D(int numIndices, int rowStart, int rowEnd, int colStart, int colEnd)	Creates a list of unique two-dimensional indices.
void	shuffle(double[] arr)	Randomly shuffles array using the Fisher–Yates algorithm.
int[]	shuffle(int[] arr)	Randomly shuffles array using the Fisher–Yates algorithm.
void	shuffle(Object[] arr)	Randomly shuffles array using the Fisher–Yates algorithm.

Methods inherited from class java.lang.Object

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

Field Details

rng

private final RandomCNumber rng

Random number generator to use when creating random arrays.

Constructor Details

RandomArray

public RandomArray()

Creates a RandomArray object to generate arrays filled with random values using a default random number generator.

RandomArray

public RandomArray(RandomCNumber rng)

Creates a RandomArray object to generate arrays filled with random values using the specified complex random number generator.

Parameters:

rng - The complex random number generator to use when creating random arrays.

Method Details

genUniformRealArray

public double[] genUniformRealArray(int length)

Generates an array of doubles filled with uniformly distributed pseudorandom values in [0.0, 1.0). To generate uniformly distributed values in a specified range see genUniformRealArray(int, double, double).

Parameters:

length - Length of pseudorandom array to generate.

Returns:

An array of doubles with specified length filled with uniformly distributed values in [0.0, 1.0).

genUniformRealArray

public double[] genUniformRealArray(int length,
 double min,
 double max)

Generates an array of doubles filled with uniformly distributed pseudorandom values in [min, max).

Parameters:

length - Length of pseudorandom array to generate.

min - Lower bound of uniform range (inclusive).

max - Upper bound of uniform range (Exclusive).

Returns:

An array of doubles with specified length filled with uniformly distributed values in [min, max).

genUniformRealIntArray

public double[] genUniformRealIntArray(int length)

Generates an array of integers filled with uniformly distributed pseudorandom int values in [Integer.MAX_VALUE, Integer.MAX_VALUE). To generate uniformly distributed values in a specified range see genUniformRealIntArray(int, int, int).

Parameters:

length - Length of pseudorandom array to generate.

Returns:

An array of integers with specified length filled with uniformly distributed values in [Integer.MAX_VALUE, Integer.MAX_VALUE).

genUniformRealIntArray

public int[] genUniformRealIntArray(int length,
 int min,
 int max)

Generates an array of integers filled with uniformly distributed pseudorandom values in [min, max).

Parameters:

length - Length of pseudorandom array to generate.

min - Lower bound of uniform range (inclusive).

max - Upper bound of uniform range (Exclusive).

Returns:

An array of integers with specified length filled with uniformly distributed values in [min, max).

genNormalRealArray

public double[] genNormalRealArray(int length)

Generates an array of doubles filled with normally pseudorandom values with a mean of 0 and standard deviation of 1.

Parameters:

length - Length of pseudorandom array to generate.

Returns:

An array of doubles with specified length filled with normally pseudorandom values with a mean of 0 and standard deviation of 1.

genNormalRealArray

public double[] genNormalRealArray(int length,
 double mean,
 double std)

Generates an array of doubles filled with normally distributed pseudorandom values with a specified mean and standard deviation.

Parameters:

length - Length of pseudorandom array to generate.

mean - Mean of normal distribution.

std - Standard deviation of normal distribution.

Returns:

An array of doubles with specified length filled with normally pseudorandom values specified mean and standard deviation.

Throws:

IllegalArgumentException - If standard deviation is negative.

genUniformComplexArray

public CNumber[] genUniformComplexArray(int length)

Generates an array of complex numbers with pseudorandom uniformly distributed magnitudes in [0.0, 1.0).

Parameters:

length - Length of the pseudorandom array to generate.

Returns:

An array of complex numbers with pseudorandom uniformly distributed magnitudes in [0.0, 1.0).

genUniformComplexArray

public CNumber[] genUniformComplexArray(int length,
 double min,
 double max)

Generates an array of pseudorandom complex numbers with uniformly distributed magnitudes in [min, max).

Parameters:

length - Length of the pseudorandom array to generate.

min - Minimum value of uniform distribution from which the magnitudes are sampled (inclusive).

max - Maximum value of uniform distribution from which the magnitudes are sampled (exclusive).

Returns:

An array of complex numbers with pseudorandom complex numbers with uniformly distributed magnitudes in [min, max).

Throws:

IllegalArgumentException - If min is negative or if max is less than min.

genNormalComplexArray

public CNumber[] genNormalComplexArray(int length)

Generates an array of complex numbers with pseudorandom normally distributed magnitudes with a mean of 0.0 and a magnitude of 1.0.

Parameters:

length - Length of the pseudorandom array to generate.

Returns:

An array of complex numbers with pseudorandom normally distributed magnitudes with a mean of 0.0 and a magnitude of 1.0.

genNormalComplexArray

public CNumber[] genNormalComplexArray(int length,
 double mean,
 double std)

Generates an array of complex numbers with pseudorandom normally distributed magnitudes with specified mean and standard deviation.

Parameters:

length - Length of the pseudorandom array to generate.

mean - Mean of the normal distribution from which to sample magnitudes.

std - Standard deviation of the normal distribution from which to sample magnitudes.

Returns:

An array of complex numbers with pseudorandom normally distributed magnitudes with specified mean and standard deviation.

Throws:

IllegalArgumentException - If standard deviation is negative.

randomUniqueIndices

public int[] randomUniqueIndices(int numIndices,
 int start,
 int end)

Creates unique indices in [start, end).

Parameters:

numIndices - Number of random unique indices to get.

start - Staring index (inclusive).

end - Ending index (exclusive).

Returns:

An array of length numIndices containing random unique indices in [start, end). The array will be sorted.

Throws:

IllegalArgumentException - If start is not in [0, end)

See Also:

• randomUniqueIndices2D(int, int, int, int, int)

randomUniqueIndices2D

public int[][] randomUniqueIndices2D(int numIndices,
 int rowStart,
 int rowEnd,
 int colStart,
 int colEnd)

Creates a list of unique two-dimensional indices.

Parameters:

numIndices - Total number of indices to generate.

rowStart - Starting row index (inclusive).

rowEnd - Ending row index (exclusive).

colStart - Starting column index (inclusive).

colEnd - Ending column index (exclusive).

Returns:

A two-dimensional array of shape 2-by-numIndices containing unique two-dimensional indices. The first row contains row indices, the second, column indices. The indices will be sorted by rows then columns.

See Also:

• randomUniqueIndices(int, int, int)

genRandomRows

private int[] genRandomRows(int numIndices,
 int rowStart,
 int rowEnd,
 int maxReps)

Helper function to generate random row indices for use in randomUniqueIndices2D(int, int, int, int, int). This method generates random row indices so that a single row is not repeated more than maxReps times.

Parameters:

numIndices - Number of indices to generate. Assumed to be less than or equal to rowEnd - rowStart.

rowStart - Minimum row index. Assumed that 0 <= rowStart < rowEnd.

rowEnd - Maximum row index. Assumed that 0 <= rowStart < rowEnd.

maxReps - Maximum number of times a single row index can be repeated.

Returns:

An array containing random row indices such that no index is repeated more than maxReps times. Note: the array is sorted before it is returned.

shuffle

public int[] shuffle(int[] arr)

Randomly shuffles array using the Fisher–Yates algorithm. This is done in place.

Parameters:

arr - Array to shuffle.

Returns:

A reference to arr.

shuffle

public void shuffle(double[] arr)

Randomly shuffles array using the Fisher–Yates algorithm. This is done in place.

Parameters:

arr - Array to shuffle.

shuffle

public void shuffle(Object[] arr)

Randomly shuffles array using the Fisher–Yates algorithm. This is done in place.

Parameters:

arr - Array to shuffle.