samoa-api/src/main/java/org/apache/samoa/moa/core/Measurement.java

package org.apache.samoa.moa.core;

/*
 * #%L
 * SAMOA
 * %%
 * Copyright (C) 2014 - 2015 Apache Software Foundation
 * %%
 * 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.
 * #L%
 */

import java.util.ArrayList;
import java.util.List;

import org.apache.samoa.moa.AbstractMOAObject;

/**
 * Class for storing an evaluation measurement.
 * 
 * @author Richard Kirkby (rkirkby@cs.waikato.ac.nz)
 * @version $Revision: 7 $
 */
public class Measurement extends AbstractMOAObject {

  private static final long serialVersionUID = 1L;

  protected String name;

  protected double value;

  public Measurement(String name, double value) {
    this.name = name;
    this.value = value;
  }

  public String getName() {
    return this.name;
  }

  public double getValue() {
    return this.value;
  }

  public static Measurement getMeasurementNamed(String name,
      Measurement[] measurements) {
    for (Measurement measurement : measurements) {
      if (name.equals(measurement.getName())) {
        return measurement;
      }
    }
    return null;
  }

  public static void getMeasurementsDescription(Measurement[] measurements,
      StringBuilder out, int indent) {
    if (measurements.length > 0) {
      StringUtils.appendIndented(out, indent, measurements[0].toString());
      for (int i = 1; i < measurements.length; i++) {
        StringUtils.appendNewlineIndented(out, indent, measurements[i].toString());
      }

    }
  }

  public static Measurement[] averageMeasurements(Measurement[][] toAverage) {
    List<String> measurementNames = new ArrayList<String>();
    for (Measurement[] measurements : toAverage) {
      for (Measurement measurement : measurements) {
        if (measurementNames.indexOf(measurement.getName()) < 0) {
          measurementNames.add(measurement.getName());
        }
      }
    }
    GaussianEstimator[] estimators = new GaussianEstimator[measurementNames.size()];
    for (int i = 0; i < estimators.length; i++) {
      estimators[i] = new GaussianEstimator();
    }
    for (Measurement[] measurements : toAverage) {
      for (Measurement measurement : measurements) {
        estimators[measurementNames.indexOf(measurement.getName())].addObservation(measurement.getValue(), 1.0);
      }
    }
    List<Measurement> averagedMeasurements = new ArrayList<Measurement>();
    for (int i = 0; i < measurementNames.size(); i++) {
      String mName = measurementNames.get(i);
      GaussianEstimator mEstimator = estimators[i];
      if (mEstimator.getTotalWeightObserved() > 1.0) {
        averagedMeasurements.add(new Measurement("[avg] " + mName,
            mEstimator.getMean()));
        averagedMeasurements.add(new Measurement("[err] " + mName,
            mEstimator.getStdDev()
                / Math.sqrt(mEstimator.getTotalWeightObserved())));
      }
    }
    return averagedMeasurements.toArray(new Measurement[averagedMeasurements.size()]);
  }

  @Override
  public void getDescription(StringBuilder sb, int indent) {
    sb.append(getName());
    sb.append(" = ");
    sb.append(StringUtils.doubleToString(getValue(), 3));
  }
}