Method: Indicators::Bb.calculate

Defined in:
lib/indicators/calculations/bb.rb

.calculate(data, parameters) ⇒ Object

Middle Band = 20-day simple moving average (SMA) Upper Band = 20-day SMA + (20-day standard deviation of price x 2) Lower Band = 20-day SMA - (20-day standard deviation of price x 2)



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# File 'lib/indicators/calculations/bb.rb', line 9

def self.calculate data, parameters
  periods = parameters[0] 
  multiplier = parameters[1]
  output = Array.new
  adj_closes = Indicators::Helper.validate_data(data, :adj_close, periods)

  adj_closes.each_with_index do |adj_close, index|
    start = index+1-periods
    if index+1 >= periods
      middle_band = Indicators::Sma.calculate(adj_closes[start..index], periods).last
      upper_band = middle_band + (adj_closes[start..index].standard_deviation * multiplier)
      lower_band = middle_band - (adj_closes[start..index].standard_deviation * multiplier)
      # Output for each point is [middle, upper, lower].
      output[index] = [middle_band, upper_band, lower_band]
    else
      output[index] = nil
    end
  end

  return output
  
end