org.apache.mahout.clustering

Class UncommonDistributions

java.lang.Object

org.apache.mahout.clustering.UncommonDistributions

public final class UncommonDistributions
extends Object

Method Summary

Modifier and Type	Method and Description
static double	rBeta(double shape1, double shape2) Returns a random sample from a beta distribution with the given shapes
static int	rBinomial(int n, double p) Returns an integer sampled according to this distribution.
static double	rGamma(double k, double lambda) Returns a double sampled according to this distribution.
static double	rNorm(double mean, double sd) Return a random value from a normal distribution with the given mean and standard deviation

Methods inherited from class java.lang.Object

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

Method Detail

rGamma

public static double rGamma(double k,
                            double lambda)

Returns a double sampled according to this distribution. Uniformly fast for all k > 0. (Reference: Non-Uniform Random Variate Generation, Devroye http://cgm.cs.mcgill.ca/~luc/rnbookindex.html) Uses Cheng's rejection algorithm (GB) for k>=1, rejection from Weibull distribution for 0 < k < 1.

rBeta

public static double rBeta(double shape1,
                           double shape2)

Returns a random sample from a beta distribution with the given shapes

Parameters:

shape1 - a double representing shape1

shape2 - a double representing shape2

Returns:

a Vector of samples

rNorm

public static double rNorm(double mean,
                           double sd)

Return a random value from a normal distribution with the given mean and standard deviation

Parameters:

mean - a double mean value

sd - a double standard deviation

Returns:

a double sample

rBinomial

public static int rBinomial(int n,
                            double p)

Returns an integer sampled according to this distribution. Takes time proportional to np + 1. (Reference: Non-Uniform Random Variate Generation, Devroye http://cgm.cs.mcgill.ca/~luc/rnbookindex.html) Second time-waiting algorithm.