/**
* Copyright 2010 Neuroph Project http://neuroph.sourceforge.net
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.neuroph.contrib;
import org.neuroph.core.transfer.TransferFunction;
/**
* Transfer function for Neuron in Interactive Activation Neural Network.
* @see org.neuroph.contrib.IACNetwork
* @see org.neuroph.contrib.IACNeuron
* @author Zoran Sevarac <sevarac@gmail.com>
* http://www.itee.uq.edu.au/~cogs2010/cmc/chapters/IAC/index2.html#Mechanism
* If the activation of a unit is equal to max then the net believes the hypothesis completely.
* If it is equal to min then the net disbelieves the hypothesis completely.
* The rest corresponds to an "I don't know state". The (max - a i) or (a i - min)
* terms ensure that the activation remains between min and max and doesn't continue to either grow
* or shrink without bound [2]. The -decay (ai - rest) part of the equation forces the activation to return
* to the rest value in the absence of external input.
*/
public class IACFunction extends TransferFunction {
private static final long serialVersionUID = 1L;
double max = 1,
min = -0.2,
rest = -0.1,
decay = 0.1;
public double getOutput(double netInput, double output) {
double delta = 0;
if (netInput>0)
delta = (max - output)*netInput - decay*(output - rest);
else
delta = (output - min)*netInput - decay*(output - rest);
output = output + delta;
return output;
}
public double getOutput(double netInput) {
throw new RuntimeException("Method getOutput(double netInput) not implemented for this type of TransferFunctions. Use getOutput(double netInput, double output)");
}
}