view src/samer/maths/random/PowerLaw.java @ 8:5e3cbbf173aa tip

Reorganise some more

/*
 *	Copyright (c) 2000, Samer Abdallah, King's College London.
 *	All rights reserved.
 *
 *	This software is provided AS iS and WITHOUT ANY WARRANTY; 
 *	without even the implied warranty of MERCHANTABILITY or 
 *	FITNESS FOR A PARTICULAR PURPOSE.
 */

package samer.maths.random;
import  samer.core.types.*;
import  java.util.*;

/*
 *		Generates random numbers from a single-sider power-law 
 *		with a lower cut-off, but no upper cut-off. The
 *		exponent must therefore be strictly less than 1.
 */
public class PowerLaw extends BaseRandom implements Observer
{
	VDouble min = new VDouble("min",1);
	VDouble D   = new VDouble("exponent",1);
	double  a, b;

	public void dispose() { min.dispose(); D.dispose(); }
	public double next() { return a*Math.pow(rnd.nextDouble(),b); }

	public PowerLaw() 
	{
		min.addObserver(this);
		D.addObserver(this);
		update(null,null);
	}

	public void update(Observable o, Object oo) {
		a=min.value;
		b=-1/D.value;
	}
}