/*
Copyright (C) 2001 Kyle Siegrist, Dawn Duehring
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 distributions;
/**This class applies a location-scale tranformation to a given distribution. In terms of
* the corresponding random variable X, the transformation is Y = a + bX*/
public class LocationScaleDistribution extends Distribution{
private Distribution dist;
private double location, scale;
/**This general constructor creates a new location-scale transformation on
a given distribuiton with given location and scale parameters*/
public LocationScaleDistribution(Distribution d, double a, double b){
setParameters(d, a, b);
}
/**This method sets the parameters: the distribution and the location and
scale parameters*/
public void setParameters(Distribution d, double a, double b){
dist = d; location = a; scale = b;
Domain domain = dist.getDomain();
double l, u, w = domain.getWidth();
int t = dist.getType();
if (t == DISCRETE){
l = domain.getLowerValue(); u = domain.getUpperValue();
}
else{
l = domain.getLowerBound(); u = domain.getUpperBound();
}
if (scale == 0) super.setParameters(location, location, 1, DISCRETE);
else if (scale < 0) super.setParameters(location + scale * u, location + scale * l, -scale * w, t);
else super.setParameters(location + scale * l, location + scale * u, scale * w, t);
}
/**This method defines the getDensity function*/
public double getDensity(double x){
if (scale == 0){
if (x == location) return 1;
else return 0;
}
else return dist.getDensity((x - location) / scale);
}
/**This method returns the maximum value of the getDensity function*/
public double getMaxDensity(){
return dist.getMaxDensity();
}
/**This mtehod returns the mean*/
public double getMean(){
return location + scale * dist.getMean();
}
/**This method returns the variance*/
public double getVariance(){
return (scale * scale) * dist.getVariance();
}
/**This method returns a simulated value from the distribution*/
public double simulate(){
return location + scale * dist.simulate();
}
/**This method returns the cumulative distribution function*/
public double getCDF(double x){
if (scale > 0) return dist.getCDF((x - location) / scale);
else return 1 - dist.getCDF((x - location) / scale);
}
/**This method returns the getQuantile function*/
public double getQuantile(double p){
if (scale > 0) return location + scale * dist.getQuantile(p);
else return location + scale * dist.getQuantile(1 - p);
}
}