Class: RoadToRubykaigi::SignalWindow::StepCadence

Inherits:
Data
  • Object
show all
Defined in:
lib/road_to_rubykaigi/signal_window.rb

Constant Summary collapse

WINDOW_SECONDS = 
2.0
MIN_STEP_INTERVAL_SECONDS =

min gap between steps (caps cadence at ~6.7Hz)

0.15
MIN_SAMPLES_FOR_LOCAL_MAXIMUM =

need prev/current/next to detect a local maximum

3

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#recent_magnitudes ⇒ Object (readonly)

Returns the value of attribute recent_magnitudes

Returns:

  • (Object) —

    the current value of recent_magnitudes



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# File 'lib/road_to_rubykaigi/signal_window.rb', line 6

def recent_magnitudes
  @recent_magnitudes
end

Instance Method Details

#hz ⇒ Object

Step cadence in Hz: count of local maxima in the recent magnitudes divided by the window duration. Walking produce one peak per footstrike, so cadence tracks step frequency.



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# File 'lib/road_to_rubykaigi/signal_window.rb', line 21

def hz
  return 0.0 if recent_magnitudes.size < MIN_SAMPLES_FOR_LOCAL_MAXIMUM

  magnitudes = recent_magnitudes.map { |entry| entry[:magnitude] }
  mean = magnitudes.sum / magnitudes.size
  step_count = 0
  last_step_time = nil
  (1...(recent_magnitudes.size - 1)).each do |i|
    time = recent_magnitudes[i][:time]
    magnitude = recent_magnitudes[i][:magnitude]
    prev_magnitude = recent_magnitudes[i - 1][:magnitude]
    next_magnitude = recent_magnitudes[i + 1][:magnitude]
    is_local_maximum = magnitude > prev_magnitude && magnitude > next_magnitude
    above_mean = magnitude > mean # only count bumps stronger than the average
    enough_gap_from_last_step = last_step_time.nil? || (time - last_step_time) >= MIN_STEP_INTERVAL_SECONDS
    if is_local_maximum && above_mean && enough_gap_from_last_step
      step_count += 1
      last_step_time = time
    end
  end

  duration = recent_magnitudes.last[:time] - recent_magnitudes.first[:time]
  return 0.0 if duration <= 0 # guard against division by zero (just in case)

  step_count / duration
end

#ready? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/road_to_rubykaigi/signal_window.rb', line 48

def ready?
  return false if recent_magnitudes.size < MIN_SAMPLES_FOR_LOCAL_MAXIMUM
  (recent_magnitudes.last[:time] - recent_magnitudes.first[:time]) >= WINDOW_SECONDS * READY_FILL_RATIO
end

#record(sample) ⇒ Object 



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# File 'lib/road_to_rubykaigi/signal_window.rb', line 11

def record(sample)
  magnitude = Math.sqrt(sample[0] ** 2 + sample[1] ** 2 + sample[2] ** 2)
  now = Time.now
  recent_magnitudes << { time: now, magnitude: magnitude }
  window_start = now - WINDOW_SECONDS
  recent_magnitudes.shift while recent_magnitudes.first[:time] < window_start
end