/*
* Encog(tm) Core v3.4 - Java Version
* http://www.heatonresearch.com/encog/
* https://github.com/encog/encog-java-core
* Copyright 2008-2016 Heaton Research, Inc.
*
* 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.
*
* For more information on Heaton Research copyrights, licenses
* and trademarks visit:
* http://www.heatonresearch.com/copyright
*/
package org.encog.util.normalize.output.multiplicative;
import org.encog.util.normalize.NormalizationError;
import org.encog.util.normalize.input.InputField;
import org.encog.util.normalize.output.OutputFieldGroup;
import org.encog.util.normalize.output.OutputFieldGrouped;
/**
* Both the multiplicative and z-axis normalization types allow a group of
* outputs to be adjusted so that the "vector length" is 1. Both go about it
* in different ways. Certain types of neural networks require a vector length
* of 1.
*
* The multiplicative normalization is more simple than Z-Axis normalization.
* Almost always Z=Axis normalization is a better choice. However,
* multiplicative can perform better than Z-Axis when all of the values
* are near zero most of the time. This can cause the "synthetic value"
* that z-axis uses to dominate and skew the answer.
*
* Multiplicative normalization works by calculating the vector length of
* the input fields and dividing each by that value. This also presents
* a problem, as the magnitude of the original fields is not used. For
* example, multiplicative normalization would not distinguish between
* (-2,1,3) and (-10,5,15). Both would result in the same output.
*
* @author jheaton
*/
public class OutputFieldMultiplicative extends OutputFieldGrouped {
/**
* The default constructor. Used for reflection.
*/
public OutputFieldMultiplicative() {
}
/**
* Construct a multiplicative output field.
* @param group The group this field belongs to.
* @param field The input field that this field is based on.
*/
public OutputFieldMultiplicative(final OutputFieldGroup group,
final InputField field) {
super(group, field);
if (!(group instanceof MultiplicativeGroup)) {
throw new NormalizationError(
"Must use MultiplicativeGroup with OutputFieldMultiplicative.");
}
}
/**
* Calculate the value for this output field.
* @param subfield The subfield is not used.
* @return The value for this field.
*/
public double calculate(final int subfield) {
return getSourceField().getCurrentValue()
/ ((MultiplicativeGroup) getGroup()).getLength();
}
/**
* @return Always returns 1, subfields are not used for this field.
*/
public int getSubfieldCount() {
return 1;
}
/**
* Not needed for this sort of output field.
*/
public void rowInit() {
}
}