Class: TechnicalAnalysis::Bb

Inherits:
Indicator show all
Defined in:
lib/technical_analysis/indicators/bb.rb

Overview

Bollinger Bands

Class Method Summary collapse

Methods inherited from Indicator

find, roster

Class Method Details

.calculate(data, period: 20, standard_deviations: 2, price_key: :value) ⇒ Array<BbValue>

Calculates the bollinger bands (BB) for the data over the given period en.wikipedia.org/wiki/Bollinger_Bands

Parameters:

  • data (Array) —

    Array of hashes with keys (:date_time, :value)

  • period (Integer) (defaults to: 20) —

    The given period to calculate the BB

  • standard_deviations (Float) (defaults to: 2) —

    The given standard deviations to calculate the upper and lower bands of the BB

  • price_key (Symbol) (defaults to: :value) —

    The hash key for the price data. Default :value

Returns:

  • (Array<BbValue>) —

    An array of BbValue instances



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# File 'lib/technical_analysis/indicators/bb.rb', line 55

def self.calculate(data, period: 20, standard_deviations: 2, price_key: :value)
  period = period.to_i
  standard_deviations = standard_deviations.to_f
  price_key = price_key.to_sym
  Validation.validate_numeric_data(data, price_key)
  Validation.validate_length(data, min_data_size(period: period))
  Validation.validate_date_time_key(data)

  data = data.sort_by { |row| row[:date_time] }

  output = []
  period_values = []

  data.each do |v|
    period_values << v[price_key]

    if period_values.size == period
      mb = ArrayHelper.average(period_values)
      sd = ArrayHelper.standard_deviation(period_values)
      ub = mb + standard_deviations * sd
      lb = mb - standard_deviations * sd

      output << BbValue.new(
        date_time: v[:date_time],
        lower_band: lb,
        middle_band: mb,
        upper_band: ub
      )

      period_values.shift
    end
  end

  output.sort_by(&:date_time).reverse
end

.indicator_name ⇒ String

Returns the name of the technical indicator

Returns:

  • (String) —

    A string of the name of the technical indicator



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# File 'lib/technical_analysis/indicators/bb.rb', line 15

def self.indicator_name
  "Bollinger Bands"
end

.indicator_symbol ⇒ String

Returns the symbol of the technical indicator

Returns:

  • (String) —

    A string of the symbol of the technical indicator



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# File 'lib/technical_analysis/indicators/bb.rb', line 8

def self.indicator_symbol
  "bb"
end

.min_data_size(period: 20, **params) ⇒ Integer

Calculates the minimum number of observations needed to calculate the technical indicator

Parameters:

  • options (Hash) —

    The options for the technical indicator

Returns:

  • (Integer) —

    Returns the minimum number of observations needed to calculate the technical indicator based on the options provided



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# File 'lib/technical_analysis/indicators/bb.rb', line 41

def self.min_data_size(period: 20, **params)
  period.to_i
end

.valid_options ⇒ Array

Returns an array of valid keys for options for this technical indicator

Returns:

  • (Array) —

    An array of keys as symbols for valid options for this technical indicator



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# File 'lib/technical_analysis/indicators/bb.rb', line 22

def self.valid_options
  %i(period standard_deviations price_key)
end

.validate_options(options) ⇒ Boolean

Validates the provided options for this technical indicator

Parameters:

  • options (Hash) —

    The options for the technical indicator to be validated

Returns:

  • (Boolean) —

    Returns true if options are valid or raises a ValidationError if they’re not



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# File 'lib/technical_analysis/indicators/bb.rb', line 31

def self.validate_options(options)
  Validation.validate_options(options, valid_options)
end