org.ojalgo.random

Class RandomUtils

java.lang.Object

org.ojalgo.random.RandomUtils

public abstract class RandomUtils
extends Object

Method Summary

Modifier and Type	Method and Description
static double	calculateVariance(double aSumOfValues, double aSumOfSquaredValues, int aValuesCount)
static double	erf(double anArg) Error Function erf() @ Wikipedia erf() @ Wolfram MathWorld
static double	erfc(double anArg) Complementary Error Function erf() @ Wikipedia erf() @ Wolfram MathWorld
static double	erfi(double anArg) Inverse Error Function erf() @ Wikipedia erf() @ Wolfram MathWorld
static double	factorial(int aVal)
static double	gamma(double arg) Lanczos approximation.
static int	partitions(int n, int[] k)
static int	permutations(int n)
static int	subsets(int n, int k)
static int	variations(int n, int k)

Methods inherited from class java.lang.Object

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

Method Detail

calculateVariance

public static double calculateVariance(double aSumOfValues,
                                       double aSumOfSquaredValues,
                                       int aValuesCount)

Parameters:

aSumOfValues - The sum of all values in a sample set

aSumOfSquaredValues - The sum of all squared values, in a sample set

aValuesCount - The number of values in the sample set

Returns:

The sample set's variance

erf

public static double erf(double anArg)

Error Function
erf() @ Wikipedia
erf() @ Wolfram MathWorld

erfc

public static double erfc(double anArg)

Complementary Error Function
erf() @ Wikipedia
erf() @ Wolfram MathWorld

erfi

public static double erfi(double anArg)

Inverse Error Function
erf() @ Wikipedia
erf() @ Wolfram MathWorld

factorial

public static double factorial(int aVal)

gamma

public static double gamma(double arg)

Lanczos approximation. The abritray constant is 7, and there are 9 coefficients used. Essentially the algorithm is taken from WikipediA , but it's modified a bit and I found more exact coefficients somewhere else.

partitions

public static int partitions(int n,
                             int[] k)

Parameters:

n - The number of elements in the set

k - A vector of subset sizes the sum of which must equal the size of the full set

Returns:

The number of ways the set can be partioned in to subsets of the given sizes

permutations

public static int permutations(int n)

Parameters:

n - The number of elements in the set

Returns:

The number of permutations of the set

subsets

public static int subsets(int n,
                          int k)

Parameters:

n - The number of elements in the set

k - The number of elements in the subset

Returns:

The number of subsets to the set

variations

public static int variations(int n,
                             int k)

Parameters:

n - The number of elements in the set

k - The size of the tuple

Returns:

The number of ordered k-tuples (variations) of the set