edu.cmu.tetrad.util.dist.LogNormal Maven / Gradle / Ivy
///////////////////////////////////////////////////////////////////////////////
// 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 org.apache.commons.math3.util.FastMath;
/**
* Represents a lognormal distribution for purposes of sampling.
*
* @author josephramsey
*/
public class LogNormal implements Distribution {
private static final long serialVersionUID = 23L;
private double sd;
public LogNormal(double sd) {
this.sd = sd;
}
/**
* Generates a simple exemplar of this class to test serialization.
*
* @return The exemplar.
*/
public static LogNormal serializableInstance() {
return new LogNormal(.5);
}
public int getNumParameters() {
return 1;
}
public String getName() {
return "LogNormal";
}
public void setParameter(int index, double value) {
if (index == 0) {
this.sd = value;
}
throw new IllegalArgumentException();
}
public double getParameter(int index) {
if (index == 0) {
return this.sd;
}
throw new IllegalArgumentException();
}
public String getParameterName(int index) {
return "Standard Deviation";
}
public double nextRandom() {
double random = RandomUtil.getInstance().nextNormal(0, this.sd);
return FastMath.exp(random);
}
public String toString() {
return "LogNormal";
}
}