org.conqat.engine.commons.machine_learning.InstanceCreatorBase.java Source code

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Here is the source code for org.conqat.engine.commons.machine_learning.InstanceCreatorBase.java

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/*-------------------------------------------------------------------------+
|                                                                          |
| Copyright 2005-2011 the ConQAT Project                                   |
|                                                                          |
| 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.conqat.engine.commons.machine_learning;

import java.util.List;

import weka.core.Attribute;
import weka.core.FastVector;

/**
 * Abstract base class to create a weka instance for a classification object of
 * type T. An instance is a representation of the classification object based on
 * features and label which is used by a machine classifier. The scheme of an
 * instance consists of attribute declarations and a class. The attributes
 * correspond to the calculated features, the class wraps all possible labels of
 * the data.
 * 
 * @author $Author: hummelb $
 * @version $Rev: 44457 $
 * @ConQAT.Rating GREEN Hash: 0B117C9D74941F1C7BA2FB370E2F4C9F
 */
public abstract class InstanceCreatorBase<T, LABEL extends Enum<LABEL>> {

    /**
     * Attribute vector needed for instance creation, contains all feature
     * values and class label.
     */
    private FastVector attributes;

    /** Set of features used to describe the classification object. */
    private final List<IFeature<T>> features;

    /** Constructor. */
    protected InstanceCreatorBase(Class<LABEL> labelClass) {
        features = getFeatures();
        createAttributeSchema(labelClass);
    }

    /** Creates a weka instance for the given classification object. */
    public weka.core.Instance createWekaInstance(T classificationObject, LABEL label) {

        // create empty instance. The size of the instance corresponds to the
        // number of features plus the class label.
        weka.core.Instance instance = new weka.core.Instance(features.size() + 1);

        // calculate features
        for (int i = 0; i < features.size(); i++) {
            instance.setValue((Attribute) attributes.elementAt(i), features.get(i).getValue(classificationObject));
        }

        // set instance label
        Attribute classAttribute = (Attribute) attributes.elementAt(attributes.size() - 1);
        instance.setValue(classAttribute, label.name());

        return instance;

    }

    /** Returns a list of features used for machine learning. */
    protected abstract List<IFeature<T>> getFeatures();

    /**
     * Sets up the weka schema of attributes and class labels for this instance.
     */
    private void createAttributeSchema(Class<LABEL> labelClass) {

        // attributes of the instance are the features and one class label
        attributes = new FastVector(features.size() + 1);

        for (IFeature<T> feature : features) {
            attributes.addElement(new Attribute(feature.getName()));
        }

        addClassAttribute(labelClass);

    }

    /**
     * Adds the class of the classification object with all possible labels to
     * the attribute vector.
     */
    private void addClassAttribute(Class<LABEL> labelClass) {

        FastVector labelVector = new FastVector(labelClass.getEnumConstants().length);

        for (LABEL label : labelClass.getEnumConstants()) {
            labelVector.addElement(label.name());
        }

        Attribute classAttribute = new Attribute("Classification Category", labelVector);
        attributes.addElement(classAttribute);
    }

    /** Returns a default label for an instance. */
    public abstract LABEL getDefaultLabel();

    /** Returns the attribute vector. */
    public FastVector getAttributes() {
        return attributes;
    }

    /** Returns the number of features. */
    public int getNumberOfFeatures() {

        return features.size();
    }
}