org.apache.commons.math.util
Class MathUtils

java.lang.Object
  org.apache.commons.math.util.MathUtils

public final class MathUtils

extends Object

Some useful additions to the built-in functions in Math.

Version:

$Revision: 1.20 $ $Date: 2004/10/14 04:01:04 $

Method Summary

static long	binomialCoefficient(int n, int k) Returns an exact representation of the Binomial Coefficient, "n choose k", the number of k-element subsets that can be selected from an n-element set.
static double	binomialCoefficientDouble(int n, int k) Returns a double representation of the Binomial Coefficient, "n choose k", the number of k-element subsets that can be selected from an n-element set.
static double	binomialCoefficientLog(int n, int k) Returns the natural log of the Binomial Coefficient, "n choose k", the number of k-element subsets that can be selected from an n-element set.
static double	cosh(double x) Returns the hyperbolic cosine of x.
static boolean	equals(double x, double y) Returns true iff both arguments are NaN or neither is NaN and they are equal
static long	factorial(int n) Returns n!.
static double	factorialDouble(int n) Returns n!.
static double	factorialLog(int n) Returns the natural logarithm of n!.
static int	hash(double value) Returns an integer hash code representing the given double value.
static byte	indicator(byte x) For a byte value x, this method returns (byte)(+1) if x >= 0 and (byte)(-1) if x < 0.
static double	indicator(double x) For a double precision value x, this method returns +1.0 if x >= 0 and -1.0 if x < 0.
static float	indicator(float x) For a float value x, this method returns +1.0F if x >= 0 and -1.0F if x < 0.
static int	indicator(int x) For an int value x, this method returns +1 if x >= 0 and -1 if x < 0.
static long	indicator(long x) For a long value x, this method returns +1L if x >= 0 and -1L if x < 0.
static short	indicator(short x) For a short value x, this method returns (short)(+1) if x >= 0 and (short)(-1) if x < 0.
static byte	sign(byte x) Returns the sign for byte value x.
static double	sign(double x) Returns the sign for double precision x.
static float	sign(float x) Returns the sign for float value x.
static int	sign(int x) Returns the sign for int value x.
static long	sign(long x) Returns the sign for long value x.
static short	sign(short x) Returns the sign for short value x.
static double	sinh(double x) Returns the hyperbolic sine of x.

Methods inherited from class java.lang.Object

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

Method Detail

sign

public static double sign(double x)

Returns the sign for double precision x.

For a double value x, this method returns +1.0 if x > 0, 0.0 if x = 0.0, and -1.0 if x < 0. Returns NaN if x is NaN.

Parameters:

x - the value, a double

Returns:

+1.0, 0.0, or -1.0, depending on the sign of x

sign

public static float sign(float x)

Returns the sign for float value x.

For a float value x, this method returns +1.0F if x > 0, 0.0F if x = 0.0F, and -1.0F if x < 0. Returns NaN if x is NaN.

Parameters:

x - the value, a float

Returns:

+1.0F, 0.0F, or -1.0F, depending on the sign of x

sign

public static byte sign(byte x)

Returns the sign for byte value x.

For a byte value x, this method returns (byte)(+1) if x > 0, (byte)(0) if x = 0, and (byte)(-1) if x < 0.

Parameters:

x - the value, a byte

Returns:

(byte)(+1), (byte)(0), or (byte)(-1), depending on the sign of x

sign

public static short sign(short x)

Returns the sign for short value x.

For a short value x, this method returns (short)(+1) if x > 0, (short)(0) if x = 0, and (short)(-1) if x < 0.

Parameters:

x - the value, a short

Returns:

(short)(+1), (short)(0), or (short)(-1), depending on the sign of x

sign

public static int sign(int x)

Returns the sign for int value x.

For an int value x, this method returns +1 if x > 0, 0 if x = 0, and -1 if x < 0.

Parameters:

x - the value, an int

Returns:

+1, 0, or -1, depending on the sign of x

sign

public static long sign(long x)

Returns the sign for long value x.

For a long value x, this method returns +1L if x > 0, 0L if x = 0, and -1L if x < 0.

Parameters:

x - the value, a long

Returns:

+1L, 0L, or -1L, depending on the sign of x

indicator

public static double indicator(double x)

For a double precision value x, this method returns +1.0 if x >= 0 and -1.0 if x < 0. Returns NaN if x is NaN.

Parameters:

x - the value, a double

Returns:

+1.0 or -1.0, depending on the sign of x

indicator

public static float indicator(float x)

For a float value x, this method returns +1.0F if x >= 0 and -1.0F if x < 0. Returns NaN if x is NaN.

Parameters:

x - the value, a float

Returns:

+1.0F or -1.0F, depending on the sign of x

indicator

public static byte indicator(byte x)

For a byte value x, this method returns (byte)(+1) if x >= 0 and (byte)(-1) if x < 0.

Parameters:

x - the value, a byte

Returns:

(byte)(+1) or (byte)(-1), depending on the sign of x

indicator

public static short indicator(short x)

For a short value x, this method returns (short)(+1) if x >= 0 and (short)(-1) if x < 0.

Parameters:

x - the value, a short

Returns:

(short)(+1) or (short)(-1), depending on the sign of x

indicator

public static int indicator(int x)

For an int value x, this method returns +1 if x >= 0 and -1 if x < 0.

Parameters:

x - the value, an int

Returns:

+1 or -1, depending on the sign of x

indicator

public static long indicator(long x)

For a long value x, this method returns +1L if x >= 0 and -1L if x < 0.

Parameters:

x - the value, a long

Returns:

+1L or -1L, depending on the sign of x

binomialCoefficient

public static long binomialCoefficient(int n,
                                       int k)

Returns an exact representation of the Binomial Coefficient, "n choose k", the number of k-element subsets that can be selected from an n-element set.

Preconditions:

• 0 <= k <= n (otherwise IllegalArgumentException is thrown)
• The result is small enough to fit into a long. The largest value of n for which all coefficients are < Long.MAX_VALUE is 66. If the computed value exceeds Long.MAX_VALUE an ArithMeticException is thrown.

Parameters:

n - the size of the set

k - the size of the subsets to be counted

Returns:

n choose k

Throws:

IllegalArgumentException - if preconditions are not met.

ArithmeticException - if the result is too large to be represented by a long integer.

binomialCoefficientDouble

public static double binomialCoefficientDouble(int n,
                                               int k)

Returns a double representation of the Binomial Coefficient, "n choose k", the number of k-element subsets that can be selected from an n-element set.

Preconditions:

• 0 <= k <= n (otherwise IllegalArgumentException is thrown)
• The result is small enough to fit into a double. The largest value of n for which all coefficients are < Double.MAX_VALUE is 1029. If the computed value exceeds Double.MAX_VALUE, Double.POSITIVE_INFINITY is returned

Parameters:

n - the size of the set

k - the size of the subsets to be counted

Returns:

n choose k

Throws:

IllegalArgumentException - if preconditions are not met.

binomialCoefficientLog

public static double binomialCoefficientLog(int n,
                                            int k)

Returns the natural log of the Binomial Coefficient, "n choose k", the number of k-element subsets that can be selected from an n-element set.

Preconditions:

• 0 <= k <= n (otherwise IllegalArgumentException is thrown)

Parameters:

n - the size of the set

k - the size of the subsets to be counted

Returns:

n choose k

Throws:

IllegalArgumentException - if preconditions are not met.

factorial

public static long factorial(int n)

Returns n!. Shorthand for n Factorial, the product of the numbers 1,...,n.

Preconditions:

• n >= 0 (otherwise IllegalArgumentException is thrown)
• The result is small enough to fit into a long. The largest value of n for which n! < Long.MAX_VALUE is 20. If the computed value exceeds Long.MAX_VALUE an ArithMeticException is thrown.

Parameters:

n - argument

Returns:

n!

Throws:

ArithmeticException - if the result is too large to be represented by a long integer.

IllegalArgumentException - if n < 0

factorialDouble

public static double factorialDouble(int n)

Returns n!. Shorthand for n Factorial, the product of the numbers 1,...,n as a double.

Preconditions:

• n >= 0 (otherwise IllegalArgumentException is thrown)
• The result is small enough to fit into a double. The largest value of n for which n! < Double.MAX_VALUE is 170. If the computed value exceeds Double.MAX_VALUE, Double.POSITIVE_INFINITY is returned

Parameters:

n - argument

Returns:

n!

Throws:

IllegalArgumentException - if n < 0

factorialLog

public static double factorialLog(int n)

Returns the natural logarithm of n!.

Preconditions:

• n >= 0 (otherwise IllegalArgumentException is thrown)

Parameters:

n - argument

Returns:

n!

Throws:

IllegalArgumentException - if preconditions are not met.

cosh

public static double cosh(double x)

Returns the hyperbolic cosine of x.

Parameters:

x - double value for which to find the hyperbolic cosine

Returns:

hyperbolic cosine of x

sinh

public static double sinh(double x)

Returns the hyperbolic sine of x.

Parameters:

x - double value for which to find the hyperbolic sine

Returns:

hyperbolic sine of x

hash

public static int hash(double value)

Returns an integer hash code representing the given double value.

Parameters:

value - the value to be hashed

Returns:

the hash code

equals

public static boolean equals(double x,
                             double y)

Returns true iff both arguments are NaN or neither is NaN and they are equal

Parameters:

x - first value

y - second value

Returns:

true if the values are equal or both are NaN