jstats
Class Statistic

java.lang.Object
  jstats.Statistic

public class Statistic

extends java.lang.Object

Statistic is the base class of the jstats package, providing a number of static methods useful for collections of data.

Version:

0.2.3

Author:

Justin Scheiber, David Edelstein

Field Summary

static java.util.Locale	locale
static int	STIRLING_THRESHOLD Numbers greater than this will have factorials computed using Stirling's Approximation

Constructor Summary

Statistic()

Method Summary

static double	combination(double n, double r) Combination function: nCr = n!
static double	factorial(double n) Performs factorial (n!)
static double	permutation(double n, double r) Permutation function: nPr = n!
static double	StirlingApproximation(double n) Stirling's Approximation for a factorial: For large values of n, n!
static double	summation(double[] values) Sum of all the values in an array.
static double	summation(long[] values) Sum of all the values in an array.

Methods inherited from class java.lang.Object

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

Field Detail

STIRLING_THRESHOLD

public static final int STIRLING_THRESHOLD

Numbers greater than this will have factorials computed using Stirling's Approximation

See Also:

Constant Field Values

locale

public static java.util.Locale locale

Constructor Detail

Statistic

public Statistic()

Method Detail

factorial

public static double factorial(double n)
                        throws StatisticException

Performs factorial (n!) function. Uses Stirling's Approximation for n > 50.

Note that n, while a double, must be an integer value; any fractional component of n is discarded before the factorial is computed; i.e., the factorial of 6.8 will be computed as a factorial of 6 (factorial(6.8) == 6!).

Parameters:

n - number to factor

Returns:

the factorial of n

Throws:

StatisticException - for n < 0

StirlingApproximation

public static double StirlingApproximation(double n)

Stirling's Approximation for a factorial: For large values of n, n! =~ n^n * e^-n * 2*PI*n.

Parameters:

n - number to factor

Returns:

Stirling's Approximation for n!

permutation

public static double permutation(double n,
                                 double r)
                          throws StatisticException

Permutation function:

nPr = n!/(n-r)!

Note that n and r, while doubles, must actually be integer values and are calculated as such; any fractional component is discarded

Parameters:

n - number of items from which to select

r - number of items in selection

Returns:

number of permutations P(n,r)

Throws:

StatisticException - if n < r or r < 0 or n < 0

combination

public static double combination(double n,
                                 double r)
                          throws StatisticException

Combination function:

nCr = n!/(n-r)!r!

Note that n and r, while doubles, must actually be integer values and are calculated as such; any fractional component is discarded

Parameters:

n - number of items from which to select

r - length of combination sequence

Returns:

number of combinations C(n,r)

Throws:

StatisticException - if n < r or n < 0 or r < 0

summation

public static double summation(double[] values)
                        throws StatisticException

Sum of all the values in an array.

Parameters:

values - an array of doubles.

Returns:

sum of all elements in the array

Throws:

StatisticException - for an empty array

summation

public static double summation(long[] values)
                        throws StatisticException

Sum of all the values in an array.

Parameters:

values - an array of longs.

Returns:

sum of all elements in the array

Throws:

StatisticException - for an empty array