Android Open Source - VTTPhysicalActivityLibrary Stability Detection

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Copyright (c) 2013, VTT Technical Research Centre of Finland All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the ...

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Java Source Code

/*
 * Copyright (c) 2013, VTT Technical Research Centre of Finland 
 * All rights reserved. /*  w  w  w  .  ja va  2s  .  com*/
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met: 
 * 
 * 1. Redistributions of source code must retain the above copyright 
 *    notice, this list of conditions and the following disclaimer. 
 * 2. Redistributions in binary form must reproduce the above copyright 
 *    notice, this list of conditions and the following disclaimer in the 
 *    documentation and/or other materials provided with the distribution. 
 * 3. Neither the name of the VTT Technical Research Centre of Finland nor the 
 *    names of its contributors may be used to endorse or promote products 
 *    derived from this software without specific prior written permission. 
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR 
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 * 
 */

package fi.vtt.physicalactivitylibrary.internal;

import fi.vtt.physicalactivitylibrary.VTTPhysicalActivityLibrary;
import java.util.ArrayList;

/**
 * Stability detection, implements DataCollectorObserver. 
 * 
 * @see  fi.vtt.physicalactivitylibrary.internal.DataCollectorObserver 
 *
 */

public final class StabilityDetection implements DataCollectorObserver {

  private double currentStabilityValueDouble;
  private double lastVarianceValueDouble;

  // Threshold value, if the variance is under this device is stabile, otherwise unstabile:

  static final double THRESHOLD_VALUE_DOUBLE = 0.03;

  public double getLastVariance() {
    return lastVarianceValueDouble;
  }

  @Override
  public double getValue() {
    return currentStabilityValueDouble;
  }

  @Override
  public int getIdentifier() {
    return VTTPhysicalActivityLibrary.DETECTION_STABILITY;
  }

  @Override
  public String getTag() {
    return "StabilityDetection";
  }

  @Override
  public void dataCollectedNotify(RawData rawDataIncoming) {
    if (!rawDataIncoming.hasAccelerometerData()) {
      // currentStabilityValueDouble = 0.0; // No data. 
      return; // Not able to continue. 
    }

    double meanDouble = 0.0;

    ArrayList<Double> valuesDoubleArrayList = new ArrayList<Double>(); // Total energy. 

    ArrayList<Float> xFloatArrayList = rawDataIncoming.getAccelerometerXBuffer();
    ArrayList<Float> yFloatArrayList = rawDataIncoming.getAccelerometerYBuffer();
    ArrayList<Float> zFloatArrayList = rawDataIncoming.getAccelerometerZBuffer();

    int accelerometerElementCountInteger = xFloatArrayList.size();

    for (int i = 0; i < accelerometerElementCountInteger; i++) {
      double valueDouble = Math.sqrt(Math.pow(xFloatArrayList.get(i), 2) + Math.pow(yFloatArrayList.get(i), 2) + Math.pow(zFloatArrayList.get(i), 2));
      meanDouble += valueDouble;

      valuesDoubleArrayList.add(valueDouble);
    }

    meanDouble = meanDouble / (double)accelerometerElementCountInteger;
    double sumDouble = 0.0;

    for (int i = 0; i < valuesDoubleArrayList.size(); i++) {
      double valueDouble = Math.pow(valuesDoubleArrayList.get(i) - meanDouble, 2);
      sumDouble += valueDouble;
    }

    double variance = sumDouble / (double) valuesDoubleArrayList.size();
    lastVarianceValueDouble = variance;

    if (variance > THRESHOLD_VALUE_DOUBLE) {
      currentStabilityValueDouble = 0.0; // Unstabile.
    }
    else {
      currentStabilityValueDouble = 1.0; // Stabile.
    }
  }

}

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