com.compomics.util.math

Class BigFunctions

java.lang.Object

com.compomics.util.math.BigFunctions

public class BigFunctions
extends Object

Functions operating with BigDecimal objects.

Author:

Marc Vaudel

Constructor Summary

Constructors

Constructor and Description
BigFunctions()

Method Summary

Modifier and Type	Method and Description
static BigDecimal	exp(BigDecimal bigDecimal, MathContext mathContext) Returns the value of the exponential of the given BigDecimal using the given MathContext.
static BigDecimal	expBD(BigDecimal x, MathContext mathContext) Returns the value of the exponential of the given BigDecimal using the given MathContext.
static BigInteger	factorial(BigInteger n) Returns n! as BigInteger.
static BigInteger	factorial(BigInteger n, BigInteger k) Returns n!/k! as BigInteger.
static BigInteger	getCombination(BigInteger k, BigInteger n) Returns the number of k-combinations in a set of n elements as a big decimal.
static BigDecimal	getMaxExp(MathContext mathContext) Returns the estimated maximal value exp can be calculated on according to the mathContext.
static BigDecimal	ln(BigDecimal bigDecimal, MathContext mathContext) Returns the natural logarithm of a big decimal.
static BigDecimal	lnBD(BigDecimal bigDecimal, MathContext mathContext) Returns the log of a big decimal.
static BigDecimal	log(BigDecimal input, double base, MathContext mathContext) Returns the log of the input in the desired base.
static BigDecimal	pow(BigDecimal x1, BigDecimal x2, MathContext mathContext) Returns the first big decimal power the second using the given math context.

Methods inherited from class java.lang.Object

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

Constructor Detail

BigFunctions

public BigFunctions()

Method Detail

factorial

public static BigInteger factorial(BigInteger n)

Returns n! as BigInteger.

Parameters:

n - a given BigInteger

Returns:

the corresponding factorial

factorial

public static BigInteger factorial(BigInteger n,
                                   BigInteger k)

Returns n!/k! as BigInteger.

Parameters:

n - a given BigInteger

k - a given BigInteger

Returns:

the corresponding factorial

getCombination

public static BigInteger getCombination(BigInteger k,
                                        BigInteger n)

Returns the number of k-combinations in a set of n elements as a big decimal.

Parameters:

k - the number of k-combinations

n - the number of elements

Returns:

the number of k-combinations in a set of n elements

ln

public static BigDecimal ln(BigDecimal bigDecimal,
                            MathContext mathContext)

Returns the natural logarithm of a big decimal. FastMath method is used when possible. Results are not rounded.

Parameters:

bigDecimal - the big decimal to estimate the log on

mathContext - the math context to use for the calculation

Returns:

the log of a big decimal

lnBD

public static BigDecimal lnBD(BigDecimal bigDecimal,
                              MathContext mathContext)

Returns the log of a big decimal. No FastMath method is used, see ln(). Results are not rounded.

Parameters:

bigDecimal - the big decimal to estimate the log on

mathContext - the math context to use for the calculation

Returns:

the log of a big decimal

log

public static BigDecimal log(BigDecimal input,
                             double base,
                             MathContext mathContext)

Returns the log of the input in the desired base. See ln method. Results are not rounded.

Parameters:

input - the input

base - the log base

mathContext - the math context to use for the calculation

Returns:

the log value of the input in the desired base.

exp

public static BigDecimal exp(BigDecimal bigDecimal,
                             MathContext mathContext)

Returns the value of the exponential of the given BigDecimal using the given MathContext. When possible, the FastMath method is used, and no rounding is performed. Results are not rounded.

Parameters:

bigDecimal - the big decimal

mathContext - the math context

Returns:

the value of the exponential of the given BigDecimal using the given MathContext

getMaxExp

public static BigDecimal getMaxExp(MathContext mathContext)

Returns the estimated maximal value exp can be calculated on according to the mathContext. Attempting to calculate exp on higher values (or lower than -value) will most likely overflow the capacity of a BigDecimal. Results are not rounded.

Parameters:

mathContext - the math context to use for the calculation

Returns:

the maximal value exp can be calculated on

expBD

public static BigDecimal expBD(BigDecimal x,
                               MathContext mathContext)

Returns the value of the exponential of the given BigDecimal using the given MathContext. FastMath method is not used, see exp(). Results are not rounded. The result is of precision p=p0-x.log(e) where p0 is the precision of the math context and log is the log 10. First order, no guarantee.

Parameters:

x - the big decimal

mathContext - the math context

Returns:

the value of the exponential of the given BigDecimal using the given MathContext

pow

public static BigDecimal pow(BigDecimal x1,
                             BigDecimal x2,
                             MathContext mathContext)

Returns the first big decimal power the second using the given math context. Results are not rounded. The precision of the result is p=p0-x2.ln(x1).log(e)-log(ln(x1)+x2) where p0 is the precision of the math context and log is the log 10. First order, no guarantee. If x1 is exact, e.g. in 10^x2, p=p0-x2.ln(x1).log(e)-log(ln(x1)) where p0 is the precision of the math context and log is the log 10. First order, no guarantee.

Parameters:

x1 - the first big decimal

x2 - the second big decimal

mathContext - the math context

Returns:

the first big decimal power the second using the given math context