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## de.jstacs.utils.random
Class RandomNumberGenerator

    java.lang.Object
      de.jstacs.utils.random.RandomNumberGenerator

All Implemented Interfaces:
  Serializable

    public class RandomNumberGenerator

extends Object
implements Serializable

Class for generating random numbers of many different distributions.
This class was written by Sundar Dorai-Raj and was downloaded from http://www.stat.vt.edu/~sundar/java/. Only a few modifications were made by Jens Keilwagen eliminating some not used variables and making the comments visible for javadoc.
RandomNumberGenerator.java Copyright (c) 2000 by Sundar Dorai-Raj
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version, provided that any use properly credits the author.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details at http://www.gnu.org
Reference. M. Matsumoto and T. Nishimura, "Mersenne Twister: A 623-Dimensionally Equidistributed Uniform Pseudo-Random Number Generator", ACM Transactions on Modeling and Computer Simulation, Vol. 8, No. 1, January 1998, pp 3--30.

Author:
  Sundar Dorai-Raj Email: sdoraira@vt.edu
See Also:
  Serialized Form

Constructor Summary
`RandomNumberGenerator()`
`RandomNumberGenerator(long seed)`

Method Summary
`protected int` | `next(int bits)`
`double` | `nextBeta(double alpha, double beta)` generates a random number from Beta(alpha,beta) (E(X)=a/(a+b) ; Var(X)=ab/[(a+b+1)(a+b)^2])
`boolean` | `nextBoolean()` generates a random boolean variable
`boolean` | `nextBoolean(double p)` generates true with probability p
`double` | `nextChiSq()` generates a random number from ChiSq(1) (E(X)=1 ; Var(X)=2)
`double` | `nextChiSq(int df)` generates a random number from ChiSq(df) (E(X)=df ; Var(X)=2*df)
`double` | `nextChiSq(int df, double lambda)` generates a random number from shifted-ChiSq(df) (E(X)=df+lambda ; Var(X)=2*df)
`double` | `nextExp()` generates a random number from Exp(1) (E(X)=1 ; Var(X)=1)
`double` | `nextExp(double beta)` generates a random number from Exp(beta) (E(X)=beta ; Var(X)=beta^2)
`double` | `nextExp(double beta, double lambda)` generates a random number from shifted-Exp(beta) (E(X)=beta+lambda ; Var(X)=beta^2)
`double` | `nextGamma()` generates a random number from Gamma(1,1) (E(X)=1 ; Var(X)=1)
`double` | `nextGamma(double alpha, double beta)` generates a random number from Gamma(alpha,beta) (E(X)=alpha*beta ; Var(X)=alpha*beta^2)
`double` | `nextGamma(double alpha, double beta, double lambda)` generates a random number from shifted-Gamma(alpha,beta) (E(X)=alpha*beta+lambda ; Var(X)=alpha*beta^2)
`double` | `nextGaussian()` generates a random number from N(0,1) (E(X)=0 ; Var(X)=1)
`double` | `nextGaussian(double m, double s2)` generates a random number from N(m,s2) (E(X)=m ; Var(X)=s2)
`int` | `nextInt()` generates an integer between 0 and 2^32
`int` | `nextInt(int n)` generates an integer between 0 and n-1 (inclusive)
`int` | `nextPoisson()` generates a random number from Poisson(1) (E(X)=1 ; Var(X)=1)
`int` | `nextPoisson(double lambda)` generates a random number from Poisson(lambda) (E(X)=lambda ; Var(X)=lambda)
`double` | `nextUniform()` generates a random number from U(0,1) (E(X)=1/2 ; Var(X)=1/12)
`double` | `nextUniform(double a, double b)` generates a random number from U(a,b) (E(X)=(b-a)/2 ; Var(X)=(b-a)^2/12)
`protected void` | `setSeed(long seed)`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### RandomNumberGenerator

    public RandomNumberGenerator()

### RandomNumberGenerator

    public RandomNumberGenerator(long seed)

Method Detail

### setSeed

    protected void setSeed(long seed)

### next

    protected int next(int bits)

### nextInt

    public int nextInt()

  generates an integer between 0 and 2^32

### nextInt

    public int nextInt(int n)

  generates an integer between 0 and n-1 (inclusive)

### nextPoisson

    public int nextPoisson(double lambda)

  generates a random number from Poisson(lambda) (E(X)=lambda ; Var(X)=lambda)

### nextPoisson

    public int nextPoisson()

  generates a random number from Poisson(1) (E(X)=1 ; Var(X)=1)

### nextBoolean

    public boolean nextBoolean()

  generates a random boolean variable

### nextBoolean

    public boolean nextBoolean(double p)

  generates true with probability p

### nextUniform

    public double nextUniform()

  generates a random number from U(0,1) (E(X)=1/2 ; Var(X)=1/12)

### nextUniform

    public double nextUniform(double a,
                              double b)

  generates a random number from U(a,b) (E(X)=(b-a)/2 ; Var(X)=(b-a)^2/12)

### nextGaussian

    public double nextGaussian()

  generates a random number from N(0,1) (E(X)=0 ; Var(X)=1)

### nextGaussian

    public double nextGaussian(double m,
                               double s2)

  generates a random number from N(m,s2) (E(X)=m ; Var(X)=s2)

### nextGamma

    public double nextGamma()

  generates a random number from Gamma(1,1) (E(X)=1 ; Var(X)=1)

### nextGamma

    public double nextGamma(double alpha,
                            double beta)

  generates a random number from Gamma(alpha,beta) (E(X)=alpha*beta ; Var(X)=alpha*beta^2)

### nextGamma

    public double nextGamma(double alpha,
                            double beta,
                            double lambda)

  generates a random number from shifted-Gamma(alpha,beta) (E(X)=alpha*beta+lambda ; Var(X)=alpha*beta^2)

### nextExp

    public double nextExp()

  generates a random number from Exp(1) (E(X)=1 ; Var(X)=1)

### nextExp

    public double nextExp(double beta)

  generates a random number from Exp(beta) (E(X)=beta ; Var(X)=beta^2)

### nextExp

    public double nextExp(double beta,
                          double lambda)

  generates a random number from shifted-Exp(beta) (E(X)=beta+lambda ; Var(X)=beta^2)

### nextChiSq

    public double nextChiSq()

  generates a random number from ChiSq(1) (E(X)=1 ; Var(X)=2)

### nextChiSq

    public double nextChiSq(int df)

  generates a random number from ChiSq(df) (E(X)=df ; Var(X)=2*df)

### nextChiSq

    public double nextChiSq(int df,
                            double lambda)

  generates a random number from shifted-ChiSq(df) (E(X)=df+lambda ; Var(X)=2*df)

### nextBeta

    public double nextBeta(double alpha,
                           double beta)

  generates a random number from Beta(alpha,beta) (E(X)=a/(a+b) ; Var(X)=ab/[(a+b+1)(a+b)^2])

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