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///////////////////////////////////////////////////////////////////////////////
// For information as to what this class does, see the Javadoc, below. //
// Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, //
// 2007, 2008, 2009, 2010, 2014, 2015, 2022 by Peter Spirtes, Richard //
// Scheines, Joseph Ramsey, and Clark Glymour. //
// //
// 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. //
// //
// 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. //
// //
// You should have received a copy of the GNU General Public License //
// along with this program; if not, write to the Free Software //
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA //
///////////////////////////////////////////////////////////////////////////////
package edu.cmu.tetrad.util.dist;
import edu.cmu.tetrad.util.RandomUtil;
import java.util.Arrays;
/**
* Wraps a chi square distribution for purposes of drawing random samples. Methods are provided to allow parameters to
* be manipulated in an interface. A value of n is returned if a number drawn uniformly from [0, 1] is less than the n +
* 1th p value.
*
* @author josephramsey
*/
public class Discrete implements Distribution {
private static final long serialVersionUID = 23L;
private final double[] p;
/**
* A discrete distribution with 0 with probability 1 - p and 1 with probability p. Each of the supplied values must
* be in (0, 1), and each must be less than its successor (if it has one).
*/
private Discrete(double... p) {
this.p = convert(p);
}
/**
* Generates a simple exemplar of this class to test serialization.
*
* @return The exemplar.
*/
@SuppressWarnings("UnusedDeclaration")
public static Discrete serializableInstance() {
return new Discrete(.1, .4, .9);
}
public int getNumParameters() {
return this.p.length;
}
public String getName() {
return "Discrete";
}
public void setParameter(int index, double value) {
this.p[index] = value;
}
public double getParameter(int index) {
return this.p[index];
}
public String getParameterName(int index) {
return "Cut #" + (index + 1);
}
public double nextRandom() {
double r = RandomUtil.getInstance().nextDouble();
for (int i = 0; i < this.p.length; i++) {
if (r < this.p[i]) return i;
}
throw new IllegalArgumentException();
}
public String toString() {
return "Discrete(" + Arrays.toString(this.p) + ")";
}
private double[] convert(double... p) {
for (double _p : p) {
if (_p < 0) throw new IllegalArgumentException("All arguments must be >= 0: " + _p);
}
double sum = 0.0;
for (double _p : p) {
sum += _p;
}
for (int i = 0; i < p.length; i++) {
p[i] = p[i] /= sum;
}
for (int i = 1; i < p.length; i++) {
p[i] = p[i - 1] + p[i];
}
return p;
}
}