Package dev.brachtendorf

Class MathUtil

java.lang.Object

dev.brachtendorf.MathUtil

public class MathUtil
extends Object

Author:

Kilian

Constructor Summary

Constructors

Constructor	Description
MathUtil()

Method Summary

Modifier and Type	Method	Description
static <T extends Number & Comparable<T>> T	clampNumber(T value, T lowerBound, T upperBound)	Clamp a number between its lower and upper bound.
static long	findClosestDivisibleInteger(int dividend, int divisor)	Find the closest value to a number which can be divided by the divisor.
static double	fitGaussian(double gaussian, double newStd, double newMean)
static double	getFractionalPart(double d)	Return the fractional part of the number
static int	getLowerShiftBitMask(int mask)	Get the right shift offset until the first masked bit
static boolean	isDoubleEquals(double needle, double target, double epsilon)	Compare two doubles.
static boolean	isNumeric(Object var)	Check if the supplied variable represents a numeric value
static double	log(double value, double base)	Returns the logarithm of an arbitrary base of a double value.
static double	normalizeValue(double value, double observedMin, double observedMax, double newMin, double newMax)	Linearly fit/transform a value from a given to a new range.
static double	normalizeValue(double value, double observedRange, double observedMax, double newRange, double newMax, boolean dummy)	Linearly fit/transform a value from a given to a new range.
static int	triangularNumber(int n)	Calculate the triangular number.

Methods inherited from class java.lang.Object

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

Constructor Detail

MathUtil

public MathUtil()

Method Detail

getLowerShiftBitMask

public static int getLowerShiftBitMask(int mask)

Get the right shift offset until the first masked bit

Parameters:

mask - bit mask to compute the offset for

Returns:

the number off bits a number needs to be shifted to be caught by the mask or -1 if the mask == 0

clampNumber

public static <T extends Number & Comparable<T>> T clampNumber(T value,
                                                               T lowerBound,
                                                               T upperBound)

Clamp a number between its lower and upper bound. If x > upper bound return upper bound. If x < lower bound return lower bound

Type Parameters:

T - The type of the input and return value

Parameters:

value - the input value

lowerBound - the lower bound

upperBound - the upper bound

Returns:

the original value if it's between bounds or the bound

Since:

1.0.0 com.github.kilianB

findClosestDivisibleInteger

public static long findClosestDivisibleInteger(int dividend,
                                               int divisor)

Find the closest value to a number which can be divided by the divisor.

 if  dividend%divisor == 0 return dividend
 if  dividend%divisor != 0 return the value closest
     to dividend which fulfills the condition
 

If two numbers are exactly the same distance away one of them will returned.

Parameters:

dividend - the dividend

divisor - the divisor

Returns:

the nearest number to dividend which can be divided by divisor

Throws:

ArithmeticException - if divisor is zero

Since:

1.0.0 com.github.kilianB

isDoubleEquals

public static boolean isDoubleEquals(double needle,
                                     double target,
                                     double epsilon)

Compare two doubles. Necessary due to non exact floating point arithmetics

Parameters:

needle - the needle

target - the target

epsilon - the amount the values may differ to still consider a match

Returns:

true if numbers are considered equal, false otherwise

Since:

1.0.0 com.github.kilianB

getFractionalPart

public static double getFractionalPart(double d)

Return the fractional part of the number

Parameters:

d - a double

Returns:

the fractional part of the number. If the base number is negative the returned fraction will also be negative.

Since:

1.0.0 com.github.kilianB

fitGaussian

public static double fitGaussian(double gaussian,
                                 double newStd,
                                 double newMean)

Parameters:

gaussian - A gaussian with std 1 and mean 0

newStd - new standard deviation

newMean - new mean

Returns:

a value fitted to the new mean and std

Since:

1.0.0 com.github.kilianB

normalizeValue

public static double normalizeValue(double value,
                                    double observedMin,
                                    double observedMax,
                                    double newMin,
                                    double newMax)

Linearly fit/transform a value from a given to a new range.

 
 [observedMin <= value <= observedMax] 
 				---> 
 [newMin <= transformed <= newMax]
 
 

Parameters:

value - The value to fit

observedMin - the minimum value of the current dataset

observedMax - the maximum value of the current dataset

newMin - the lower end of the newly fitted range

newMax - the upper end of the newly fitted range

Returns:

the transformed value

normalizeValue

public static double normalizeValue(double value,
                                    double observedRange,
                                    double observedMax,
                                    double newRange,
                                    double newMax,
                                    boolean dummy)

Linearly fit/transform a value from a given to a new range.

 
 [observedMin <= value <= observedMax] 
 				---> 
 [newMin <= transformed <= newMax]
 
 

This method uses a the pre computed range instead of the single range bounds to minimize repetitive calculations in case this method gets called multiple times. For more convenient arguments take a look at normalizeValue(double, double, double, double, double);

Parameters:

value - The value to fit

observedRange - the observedMax - observedMin

observedMax - the maximum value of the current dataset

newRange - the newMax - newMin

newMax - the upper end of the newly fitted range

dummy - dummy variables used to prevent ambiguous method signatures

Returns:

the transformed value

isNumeric

public static boolean isNumeric(Object var)

Check if the supplied variable represents a numeric value

Parameters:

var - the variable to check

Returns:

true if the variable is a number, false otherwise

Since:

1.2.0 com.github.kilianB

log

public static double log(double value,
                         double base)

Returns the logarithm of an arbitrary base of a double value. Special cases:

• If the argument is NaN or less than zero, then the result is NaN.
• If the argument is positive infinity, then the result is positive infinity.
• If the argument is positive zero or negative zero, then the result is negative infinity.
• If the base is zero or NaN the result is NaN

Parameters:

value - the value of the logarithm

base - the base of the logarithm

Returns:

the log_base(value)

Since:

1.3.2 com.github.kilianB

triangularNumber

public static int triangularNumber(int n)

Calculate the triangular number. The triangular sum is the sum of all positive natural number up to n. The triangular number (n-1) represents the number of distinct 2 element sets that can be constructed given n individuals. 1 + 2 + 3 + 4 + ... + n The method is undefined for n < 1

Parameters:

n - the number up to which the numbers are summed up

Returns:

the triangular number

Throws:

ArithmeticException - if n is 0

Since:

1.4.1 com.github.kilianB