org.locationtech.jts.math

Class MathUtil

java.lang.Object

org.locationtech.jts.math.MathUtil

public class MathUtil
extends Object

Various utility functions for mathematical and numerical operations.

Author:

mbdavis

Field Summary

Fields

Modifier and Type	Field and Description
static double	PHI_INV The inverse of the Golden Ratio phi.

Constructor Summary

Constructors

Constructor and Description
MathUtil()

Method Summary

Modifier and Type	Method and Description
static double	average(double x1, double x2) Computes the average of two numbers.
static int	ceil(int num, int denom) Computes the ceiling function of the dividend of two integers.
static double	clamp(double x, double min, double max) Clamps a double value to a given range.
static int	clamp(int x, int min, int max) Clamps an int value to a given range.
static int	clampMax(int x, int max) Clamps an integer to a given maximum limit.
static double	log10(double x) Computes the base-10 logarithm of a double value.
static double	max(double v1, double v2, double v3)
static double	max(double v1, double v2, double v3, double v4)
static double	min(double v1, double v2, double v3, double v4)
static double	quasirandom(double curr) Generates a quasi-random sequence of numbers in the range [0,1].
static double	quasirandom(double curr, double alpha) Generates a quasi-random sequence of numbers in the range [0,1].
static int[]	shuffle(int n) Generates a randomly-shuffled list of the integers from [0..n-1].
static int	wrap(int index, int max) Computes an index which wraps around a given maximum value.

Methods inherited from class java.lang.Object

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

Field Detail

PHI_INV

public static final double PHI_INV

The inverse of the Golden Ratio phi.

Constructor Detail

MathUtil

public MathUtil()

Method Detail

clamp

public static double clamp(double x,
                           double min,
                           double max)

Clamps a double value to a given range.

Parameters:

x - the value to clamp

min - the minimum value of the range

max - the maximum value of the range

Returns:

the clamped value

clamp

public static int clamp(int x,
                        int min,
                        int max)

Clamps an int value to a given range.

Parameters:

x - the value to clamp

min - the minimum value of the range

max - the maximum value of the range

Returns:

the clamped value

clampMax

public static int clampMax(int x,
                           int max)

Clamps an integer to a given maximum limit.

Parameters:

x - the value to clamp

max - the maximum value

Returns:

the clamped value

ceil

public static int ceil(int num,
                       int denom)

Computes the ceiling function of the dividend of two integers.

Parameters:

num - the numerator

denom - the denominator

Returns:

the ceiling of num / denom

log10

public static double log10(double x)

Computes the base-10 logarithm of a double value.

• 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.

Parameters:

x - a positive number

Returns:

the value log a, the base-10 logarithm of the input value

wrap

public static int wrap(int index,
                       int max)

Computes an index which wraps around a given maximum value. For values >= 0, this is equals to val % max. For values < 0, this is equal to max - (-val) % max

Parameters:

index - the value to wrap

max - the maximum value (or modulus)

Returns:

the wrapped index

average

public static double average(double x1,
                             double x2)

Computes the average of two numbers.

Parameters:

x1 - a number

x2 - a number

Returns:

the average of the inputs

max

public static double max(double v1,
                         double v2,
                         double v3)

max

public static double max(double v1,
                         double v2,
                         double v3,
                         double v4)

min

public static double min(double v1,
                         double v2,
                         double v3,
                         double v4)

quasirandom

public static double quasirandom(double curr)

Generates a quasi-random sequence of numbers in the range [0,1]. They are produced by an additive recurrence with 1/φ as the constant. This produces a low-discrepancy sequence which is more evenly distribute than random numbers.

See Wikipedia: Low-discrepancy Sequences - Additive Recurrence.

The sequence is initialized by calling it with any positive fractional number; 0 works well for most uses.

Parameters:

curr - the current number in the sequence

Returns:

the next value in the sequence

quasirandom

public static double quasirandom(double curr,
                                 double alpha)

Generates a quasi-random sequence of numbers in the range [0,1]. They are produced by an additive recurrence with constant α.

     R(α) :  tn = { t0 + nα },  n = 1,2,3,...   
 

When α is irrational this produces a Low discrepancy sequence which is more evenly distributed than random numbers.

The sequence is initialized by calling it with any positive fractional number. 0 works well for most uses.

Parameters:

curr - the current number in the sequence

alpha - the sequence additive constant

Returns:

the next value in the sequence

shuffle

public static int[] shuffle(int n)

Generates a randomly-shuffled list of the integers from [0..n-1].

One use is to randomize points inserted into a KDtree.

Parameters:

n - the number of integers to shuffle

Returns:

the shuffled array