package mikera.vectorz.ops;

import java.io.ObjectStreamException;

import mikera.vectorz.AVector;

public final class Logistic extends ABoundedOp {
	
	public static final Logistic INSTANCE=new Logistic();
	
	public static double logisticFunction(double a) {
		double ea=Math.exp(-a);
		double df=(1/(1.0f+ea));
		if (Double.isNaN(df)) return (a>0)?1:0;
		return df;
	}
	
	private static double inverseLogistic (double a) {
		if (a>=1) return 800;
		if (a<=0) return -800;
		double ea=a/(1.0-a);
		return Math.log(ea);
	}
	
	@Override
	public double apply(double x) {
		return logisticFunction(x);
	}
	
	@Override
	public double applyInverse(double y) {
		return inverseLogistic(y);
	}
	
	@Override
	public void applyTo(double[] data, int start,int length) {
		for (int i=0; i