org.daisy.common.fuzzy.MembershipFunctions Maven / Gradle / Ivy
package org.daisy.common.fuzzy;
import com.google.common.base.Function;
public class MembershipFunctions{
public static Function newTrapezoidFunction(double x1, double x2, double x3,double x4){
return TrapezoidFunction.fromPoints(x1,x2,x3,x4);
}
public static Function newEqualsFunction(final double value){
return new Function() {
@Override
public Double apply(Double otherValue) {
return (otherValue==value)? 1.0:0.0;
}
};
}
//Protected classes
/**
* A fuzzy set which basically have this shape
* -------- 1
* / \
* / \
* / \ 0
*/
static class TrapezoidFunction implements Function{
private double []points;
private TrapezoidFunction(double []points){
this.points=points;
}
/**
* Creates a new trapezoidal memebership function from four points defining the start, end of the first slope, start of the last slope and the ending point.
* x1<=x2<=x3<=x4
*/
public static TrapezoidFunction fromPoints(double x1, double x2, double x3,double x4){
if (!(x1<=x2 && x2<=x3 && x3<=x4)){
throw new IllegalArgumentException(String.format("Fuzzy set boundaries are not x1<=x2<=x3<=x4 (%s, %s, %s, %s)",
x1,x2,x3,x4));
}
return new TrapezoidFunction(new double[]{x1,x2,x3,x4});
}
@Override
/**
* Computes the memebership value
*/
public Double apply(Double x) {
double res=-1;
int seg=getSegment(x);
switch(seg){
case -1:
res=0;
break;
case 0: //(x-x_0)/(x_1-x_0)
res=(x-this.points[seg])/(this.points[seg+1]-this.points[seg]);
if (Double.isNaN(res))
res=1;
break;
case 1:
res=1;
break;
case 2://(x1-x)/(x_1-x_0)
res=(this.points[seg+1]-x)/(this.points[seg+1]-this.points[seg]);
if (Double.isNaN(res))
res=1;
break;
}
return new Double(res);
}
/**
* Returns the segment index where this vlaue falls into. -1 is out of the bounds
*
*/
int getSegment(double x){
if (x<0.0 ){
x=0;
}else if (x>1.0){
x=1;
}
for (int i=0;i=this.points[segment] && x<=this.points[segment+1]);
}
}
}