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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.io.IOException;
import java.io.ObjectInputStream;
/**
* Wraps a chi square distribution for purposes of drawing random samples. Methods are provided to allow parameters to
* be manipulated in an interface. See Wikipedia.
*
* @author josephramsey
*/
public class ChiSquare implements Distribution {
private static final long serialVersionUID = 23L;
/**
* The stored degees of freedom. Needed because the wrapped distribution does not provide getters for its
* parameters.
*/
private double df = 5.0;
/**
* Constructs a new Chi Square distribution.
*/
private ChiSquare() {
this.df = 5.0;
}
/**
* Generates a simple exemplar of this class to test serialization.
*
* @return the exemplar.
*/
@SuppressWarnings("UnusedDeclaration")
public static ChiSquare serializableInstance() {
return new ChiSquare();
}
public void setParameter(int index, double value) {
if (index == 0 && value >= 0.0) {
this.df = value;
} else {
throw new IllegalArgumentException("Illegal value: " + index + " = " + value);
}
}
public double getParameter(int index) {
if (index == 0) {
return this.df;
} else {
throw new IllegalArgumentException("Illegal index: " + index);
}
}
public String getParameterName(int index) {
if (index == 0) {
return "DF";
} else {
throw new IllegalArgumentException("Not a parameter index: " + index);
}
}
public int getNumParameters() {
return 1;
}
public String getName() {
return "Chi Square";
}
public double nextRandom() {
return RandomUtil.getInstance().nextChiSquare(this.df);
}
public String toString() {
return "ChiSquare(" + this.df + ")";
}
/**
* Adds semantic checks to the default deserialization method. This method must have the standard signature for a
* readObject method, and the body of the method must begin with "s.defaultReadObject();". Other than that, any
* semantic checks can be specified and do not need to stay the same from version to version. A readObject method of
* this form may be added to any class, even if Tetrad sessions were previously saved out using a version of the
* class that didn't include it. (That's what the "s.defaultReadObject();" is for. See J. Bloch, Effective Java, for
* help.
*
* @param s Ibid.
* @throws java.io.IOException If the stream cannot be read.
* @throws ClassNotFoundException If the class of an object in the stream is not in the project.
*/
private void readObject(ObjectInputStream s)
throws IOException, ClassNotFoundException {
s.defaultReadObject();
}
}