/**
** StatsTools.java
**
** Copyright 2011 by Joseph Harrison, Mark Coletti, Cristina Metgher, Andrew Crooks
** George Mason University.
**
** Licensed under the Academic Free License version 3.0
**
** See the file "LICENSE" for more information
**
** *$Id$
**/
package sim.app.geo.sickStudents;
public class StatsTools
{
static public double calcLognormalMu(double mean, double stdev) {
return Math.log(mean) - 0.5 * Math.log(1.0 + (stdev*stdev) / (mean*mean));
}
static public double calcLognormalSigma(double mean, double stdev) {
return Math.sqrt(Math.log((stdev*stdev) / (mean*mean) + 1.0));
}
/**
* Convert a random variable drawn from a normal (Gaussian) distribution to
* one that is lognormally distributed.
* @param mu
* @param sigma
* @param normalVal random number drawn from a normal distribution.
* @return
*/
static public double normalToLognormal(double mu, double sigma, double normalVal) {
return Math.exp(mu + sigma*normalVal);
}
}