moving_average_hanning.r2py

"""
<Program Name>
  moving_average_hanning.r2py

<Purpose>
  This is a script for hanning moving average filter to filter out 
  the raw acceleration data. Introducing an preset maximum 
  sample interval to avoid device lag.
"""




# output: y[n] = (x[n] + 2*x[n-1] + x[n-2])/4
# the delay = 1 sample
class HanningFilter:
  def __init__(self, current_time, threshold):
    self.mag_list = []
    self.window_size = 2
    self.last_time = current_time
    self.threshold = threshold



  def hanning_filter(self, data, current_time):
    # avoid device lag
    # different sampling time interval will reduce the filter's accuracy
    if current_time - self.last_time > self.threshold:
      self.mag_list = []
    length = len(self.mag_list)

    


    if length < self.window_size:
      self.mag_list.append(data)
      filtered_magNoG = data

    else:
      filtered_magNoG = (self.mag_list[0] + 2 * self.mag_list[1] + data)/4
      self.mag_list[0] = self.mag_list[1]
      self.mag_list[1] = data


    self.last_time = current_time


    return filtered_magNoG



# -*- mode: python;-*-