streams.weka.QFactor Maven / Gradle / Ivy

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/**
 * 
 */
package streams.weka;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import stream.AbstractProcessor;
import stream.Data;
import stream.annotations.Parameter;
import stream.data.Statistics;

/**
 * This implementation of a processor will compute the *q-factor*, i.e. the
 * efficiency of the class prediction for the positive class. The true label of
 * the instances is expected to be found as key `@label` whereas the predicted
 * value is assumed to be available as `@prediction`.
 * 
 * @author Christian Bockermann <[email protected]>
 * 
 */
public class QFactor extends AbstractProcessor {

	static Logger log = LoggerFactory.getLogger(QFactor.class);

	@Parameter(description = "The key under which the true label of the item is found.", required = false, defaultValue = "@label")
	String label = "@label";

	@Parameter(description = "The key under which the predicted class value is found.", required = false, defaultValue = "@prediction")
	String prediction = "@prediction";

	final Statistics statistics = new Statistics();

	/**
	 * @see stream.Processor#process(stream.Data)
	 */
	@Override
	public Data process(Data input) {

		if (input.containsKey(prediction) && input.containsKey(label)) {

			String label = input.get(this.label).toString();
			String pred = input.get(this.prediction).toString();

			if (label.equals("gamma")) {

				if (label.equals(pred)) {
					statistics.add("true-positive", 1.0d);
				} else {
					statistics.add("false-positive", 1.0d);
				}

			} else {
				if (label.equals(pred)) {
					statistics.add("true-negative", 1.0d);
				} else {
					statistics.add("false-negative", 1.0d);
				}
			}
		}

		return input;
	}

	/**
	 * @see stream.AbstractProcessor#finish()
	 */
	@Override
	public void finish() throws Exception {
		super.finish();

		Double tp = value("true-positive");
		Double fp = value("false-positive");
		Double tn = value("true-negative");
		Double fn = value("false-negative");

		Double q = qfactor(tp, fp, tn, fn);
		log.info("+----- Q-Factor -----");
		log.info("|  TP = {}", tp);
		log.info("|  FP = {}", fp);
		log.info("|  TN = {}", tn);
		log.info("|  FN = {}", fn);
		log.info("|");
		log.info("|   q-Factor:  {}", q);
		log.info("+----- -------- -----");
	}

	/**
	 * @return the label
	 */
	public String getLabel() {
		return label;
	}

	/**
	 * @param label
	 *            the label to set
	 */
	public void setLabel(String label) {
		this.label = label;
	}

	/**
	 * @return the prediction
	 */
	public String getPrediction() {
		return prediction;
	}

	/**
	 * @param prediction
	 *            the prediction to set
	 */
	public void setPrediction(String prediction) {
		this.prediction = prediction;
	}

	protected Double value(String key) {
		Double val = statistics.get(key);
		if (val == null) {
			return 0.0;
		} else {
			return val;
		}
	}

	public static double qfactor(double tp, double fp, double tn, double fn) {
		return (tp / (tp + fn)) / Math.sqrt(fp / (fp + tn));
	}
}