uk.ac.ed.inf.utils.stats
Class TruncatedPareto

java.lang.Object
  cern.colt.PersistentObject
      cern.jet.random.AbstractDistribution
          cern.jet.random.AbstractContinousDistribution
              cern.jet.random.Pareto
                  uk.ac.ed.inf.utils.stats.TruncatedPareto

All Implemented Interfaces:

DoubleFunction, IntFunction, java.io.Serializable, java.lang.Cloneable

Direct Known Subclasses:

PseudoTruncatedPareto

public class TruncatedPareto
extends Pareto

A utility class to extract from a truncated Pareto (power-law, long-tail) distribution. Numbers are extracted from a standard Pareto distribution. If the number extracted in above the truncation threshold, another extraction is performed. http://en.wikipedia.org/wiki/Pareto_distribution

Version:

19 Jul 2008

Author:

Luna De Ferrari luna.deferrari-at-ed.ac.uk

See Also:

Serialized Form

Constructor Summary

TruncatedPareto(double scale, double shape, int offset, int truncationThreshold)

Method Summary

int	getOffset()
Pareto	getPareto()
java.util.TreeMap<java.lang.Integer,java.lang.Integer>	getParetoFrequencies(int numberOfExtractions) Extracts numbers from a pareto distribution for the given number of times and records the freqencies with which the integers have been extracted
int	getTruncationThreshold()
int	nextInt() Returns a random number from the distribution; returns (int) Math.round(nextDouble()).

Methods inherited from class cern.jet.random.Pareto

cdf, nextDouble, nextDouble, pdf, setState, staticNextDouble, toString

Methods inherited from class cern.jet.random.AbstractDistribution

apply, apply, clone, makeDefaultGenerator

Methods inherited from class java.lang.Object

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

Constructor Detail

TruncatedPareto

public TruncatedPareto(double scale,
                       double shape,
                       int offset,
                       int truncationThreshold)

Parameters:

scale - the distribution scale

shape - the distribution shape

offset - an offset (all extracted numbers will start from the offset)

truncationThreshold - a truncation threshold (no extracted number will be above the threshold)

Method Detail

getOffset

public int getOffset()

getPareto

public Pareto getPareto()

getParetoFrequencies

public java.util.TreeMap<java.lang.Integer,java.lang.Integer> getParetoFrequencies(int numberOfExtractions)

Extracts numbers from a pareto distribution for the given number of times and records the freqencies with which the integers have been extracted

Parameters:

numberOfExtractions - the number of integer extractions from a a pareto distribution

Returns:

a map containing an integer as key and a frequency as value (frequency = number of times the integer has been extracted)

getTruncationThreshold

public int getTruncationThreshold()

nextInt

public int nextInt()

Description copied from class: AbstractDistribution

Returns a random number from the distribution; returns (int) Math.round(nextDouble()). Override this method if necessary.

Overrides:

nextInt in class AbstractDistribution