SlopeTimeAverager.java

package org.fluxoid.utils;

public class SlopeTimeAverager implements Averager {

  public static final int NUMBER_OF_VALUES_TO_AVERAGE = 10;
  Long timeOffset;
  Double lastTimeStamp;
  double lastValue;
  Double thresholdMax;
  Double thresholdMin;

  private RunningAverager runningAverager = new RunningAverager(NUMBER_OF_VALUES_TO_AVERAGE);


  @Override
  public void add(double y) {
    if (timeOffset == null) {
      timeOffset = System.nanoTime();
    }

    double timestamp = getTimeStamp();

    // handle initial case where no previous timestamp exists
    if (lastTimeStamp == null) {
      lastTimeStamp = timestamp;
      lastValue = y;
      return;
    }

    double rise = y - lastValue;
    double run = timestamp - lastTimeStamp;

    runningAverager.add(rise / run);

  }

  /**
   * Timestamp in seconds
   *
   * @return timestamp
   */
  protected double getTimeStamp() {
    double timestamp = System.nanoTime() / Math.pow(10, 9); //seconds
    return timestamp;
  }

  @Override
  public Double getLastValue() {
    return runningAverager.getLastValue();
  }

  @Override
  public double getAverage() {
    return runningAverager.getAverage();
  }

  public void setThreshold(Double max, Double min) {
    thresholdMax = max;
    thresholdMin = min;
  }

  protected boolean isBelowMaxThreshold() {
    if (thresholdMax == null) return true;
    if (getAverage() <= thresholdMax) return true;
    return false;
  }

  protected boolean isAboveMinThreshold() {
    if (thresholdMin == null) return true;
    if (getAverage() >= thresholdMin) return true;
    return false;
  }

  public boolean isWithinThreshold() {
    return (isBelowMaxThreshold() && isAboveMinThreshold());
  }

  //TODO: auto reset if not updated within certain time frame
  // setAutoReset(Double timeInSeconds) - null disable
  // or sucession of same value?

  public static void main(String[] args) {
    SlopeTimeAverager sa = new SlopeTimeAverager() {
      double timestamp = 0;

      protected double getTimeStamp() {
        timestamp += 1.; //seconds
        return timestamp;
      }
    };

    sa.add(0);
    sa.add(1);
    sa.add(2);
    sa.add(3);
    sa.add(10);
    sa.add(5);

    System.out.println(sa.getAverage());
  }

  @Override
  public int getNumberOfSamples() {
    return runningAverager.getNumberOfSamples();
  }
}