com.threerings.media.util

Class MathUtil

java.lang.Object

com.threerings.media.util.MathUtil

public class MathUtil
extends Object

Provides miscellaneous useful utility routines for mathematical calculations.

Constructor Summary

Constructors

Constructor and Description
MathUtil()

Method Summary

Modifier and Type	Method and Description
static int	bound(int low, int value, int high) Bounds the supplied value within the specified range.
static int	choose(int n, int k) Computes (N choose K), the number of ways to select K different elements from a set of size N.
static float	distance(int x0, int y0, int x1, int y1) Return the distance between the given points.
static float	distance(Point source, Point dest) Return the distance between the given points.
static int	distanceSq(int x0, int y0, int x1, int y1) Return the squared distance between the given points.
static double	ellipseCircum(double a, double b) Returns the approximate circumference of the ellipse defined by the specified minor and major axes.
static int	floorDiv(int dividend, int divisor) Computes the floored division dividend/divisor which is useful when dividing potentially negative numbers into bins.
static String	lineToString(int x0, int y0, int x1, int y1) Return a string representation of the given line.
static String	lineToString(Point p1, Point p2) Return a string representation of the given line.
static int	sign(int value) Returns positive 1 if the sign of the argument is positive, or -1 if the sign of the argument is negative.
static float[]	stddev(int[] values, int start, int length) Computes the standard deviation of the supplied values.

Methods inherited from class java.lang.Object

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

Constructor Detail

MathUtil

public MathUtil()

Method Detail

bound

public static int bound(int low,
                        int value,
                        int high)

Bounds the supplied value within the specified range.

Returns:

low if value < low, high if value > high and value otherwise.

distanceSq

public static int distanceSq(int x0,
                             int y0,
                             int x1,
                             int y1)

Return the squared distance between the given points.

distance

public static float distance(int x0,
                             int y0,
                             int x1,
                             int y1)

Return the distance between the given points.

distance

public static float distance(Point source,
                             Point dest)

Return the distance between the given points.

lineToString

public static String lineToString(int x0,
                                  int y0,
                                  int x1,
                                  int y1)

Return a string representation of the given line.

lineToString

public static String lineToString(Point p1,
                                  Point p2)

Return a string representation of the given line.

ellipseCircum

public static double ellipseCircum(double a,
                                   double b)

Returns the approximate circumference of the ellipse defined by the specified minor and major axes. The formula used (due to Ramanujan, via a paper of his entitled "Modular Equations and Approximations to Pi"), is Pi(3a + 3b - sqrt[(a+3b)(b+3a)]).

sign

public static int sign(int value)

Returns positive 1 if the sign of the argument is positive, or -1 if the sign of the argument is negative.

floorDiv

public static int floorDiv(int dividend,
                           int divisor)

Computes the floored division dividend/divisor which is useful when dividing potentially negative numbers into bins.

For example, the following numbers floorDiv 10 are:

 -15 -10 -8 -2 0 2 8 10 15
  -2  -1 -1 -1 0 0 0  1  1
 

stddev

public static float[] stddev(int[] values,
                             int start,
                             int length)

Computes the standard deviation of the supplied values.

Returns:

an array of three values: the mean, variance and standard deviation, in that order.

choose

public static int choose(int n,
                         int k)

Computes (N choose K), the number of ways to select K different elements from a set of size N.