gps.util
Class PowerLaw

java.lang.Object
  gps.util.PowerLaw

public class PowerLaw
extends java.lang.Object

provides power law selection. Modified by Weishuai Yang this file is based on T J Finney's Manuscripts Simulation Tool, 2001

Constructor Summary

PowerLaw()
constructs a power law object using an internal random generator

PowerLaw(java.util.Random r)
constructs a power law object using an external random generator

Method Summary

double	getRand() get uniformly distributed double in [0, 1]
int	getRandInt(int N) get uniformly distributed integer in [0, N - 1]
static void	main(java.lang.String[] args) test purpose main
int	select(double[] nums, double p) selects item using power law probability of selecting array item: p(ni) = k * (ni^p) k is a normalisation constant p(ni) = 0 if ni is zero, even when p < 0
int	zipf(int size) select item using Zipf's law

Methods inherited from class java.lang.Object

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

Constructor Detail

PowerLaw

public PowerLaw(java.util.Random r)

constructs a power law object using an external random generator

Parameters:

r - random generator passed in

PowerLaw

public PowerLaw()

constructs a power law object using an internal random generator

Method Detail

getRand

public double getRand()

get uniformly distributed double in [0, 1]

getRandInt

public int getRandInt(int N)

get uniformly distributed integer in [0, N - 1]

select

public int select(double[] nums,
                  double p)

selects item using power law probability of selecting array item: p(ni) = k * (ni^p) k is a normalisation constant p(ni) = 0 if ni is zero, even when p < 0

Parameters:

nums - array of numbers ni

p - exponent p

Returns:

index in [0, array size - 1]

zipf

public int zipf(int size)

select item using Zipf's law

Parameters:

size - of ranked array

Returns:

index in [0, array size - 1]

main

public static void main(java.lang.String[] args)

test purpose main

Parameters:

args - command line inputs