Class: FieldTest::Experiment

Inherits:
Object
  • Object
show all
Defined in:
lib/field_test/experiment.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(attributes) ⇒ Experiment

Returns a new instance of Experiment.



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# File 'lib/field_test/experiment.rb', line 5

def initialize(attributes)
  attributes = attributes.symbolize_keys
  @id = attributes[:id]
  @name = attributes[:name] || @id.to_s.titleize
  @variants = attributes[:variants]
  @winner = attributes[:winner]
  @started_at = Time.zone.parse(attributes[:started_at].to_s) if attributes[:started_at]
  @ended_at = Time.zone.parse(attributes[:ended_at].to_s) if attributes[:ended_at]
end

Instance Attribute Details

#ended_at ⇒ Object (readonly)

Returns the value of attribute ended_at.



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# File 'lib/field_test/experiment.rb', line 3

def ended_at
  @ended_at
end

#id ⇒ Object (readonly)

Returns the value of attribute id.



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# File 'lib/field_test/experiment.rb', line 3

def id
  @id
end

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/field_test/experiment.rb', line 3

def name
  @name
end

#started_at ⇒ Object (readonly)

Returns the value of attribute started_at.



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# File 'lib/field_test/experiment.rb', line 3

def started_at
  @started_at
end

#variants ⇒ Object (readonly)

Returns the value of attribute variants.



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# File 'lib/field_test/experiment.rb', line 3

def variants
  @variants
end

#winner ⇒ Object (readonly)

Returns the value of attribute winner.



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# File 'lib/field_test/experiment.rb', line 3

def winner
  @winner
end

Class Method Details

.all ⇒ Object 



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# File 'lib/field_test/experiment.rb', line 112

def self.all
  FieldTest.config["experiments"].map do |id, settings|
    FieldTest::Experiment.new(settings.merge(id: id.to_s))
  end
end

.find(id) ⇒ Object

Raises:



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# File 'lib/field_test/experiment.rb', line 105

def self.find(id)
  experiment = all.index_by(&:id)[id.to_s]
  raise FieldTest::ExperimentNotFound unless experiment

  experiment
end

Instance Method Details

#active? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/field_test/experiment.rb', line 101

def active?
  !winner
end

#convert(participants) ⇒ Object 



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# File 'lib/field_test/experiment.rb', line 42

def convert(participants)
  participants = FieldTest::Participant.standardize(participants)
  membership = membership_for(participants)

  if membership
    membership.converted = true
    membership.save! if membership.changed?
    true
  else
    false
  end
end

#memberships ⇒ Object 



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# File 'lib/field_test/experiment.rb', line 55

def memberships
  FieldTest::Membership.where(experiment: id)
end

#results ⇒ Object 



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# File 'lib/field_test/experiment.rb', line 59

def results
  data = memberships.group(:variant).group(:converted)
  data = data.where("created_at >= ?", started_at) if started_at
  data = data.where("created_at <= ?", ended_at) if ended_at
  data = data.count
  results = {}
  variants.each do |variant|
    converted = data[[variant, true]].to_i
    participated = converted + data[[variant, false]].to_i
    results[variant] = {
      participated: participated,
      converted: converted,
      conversion_rate: participated > 0 ? converted.to_f / participated : nil
    }
  end
  case variants.size
  when 1
    results[variants[0]][:prob_winning] = 1
  when 2, 3
    variants.size.times do |i|
      c = results.values[i]
      b = results.values[(i + 1) % variants.size]
      a = results.values[(i + 2) % variants.size]

      alpha_a = 1 + a[:converted]
      beta_a = 1 + a[:participated] - a[:converted]
      alpha_b = 1 + b[:converted]
      beta_b = 1 + b[:participated] - b[:converted]
      alpha_c = 1 + c[:converted]
      beta_c = 1 + c[:participated] - c[:converted]

      results[variants[i]][:prob_winning] =
        if variants.size == 2
          prob_b_beats_a(alpha_b, beta_b, alpha_c, beta_c)
        else
          prob_c_beats_a_and_b(alpha_a, beta_a, alpha_b, beta_b, alpha_c, beta_c)
        end
    end
  end
  results
end

#variant(participants, options = {}) ⇒ Object 



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# File 'lib/field_test/experiment.rb', line 15

def variant(participants, options = {})
  return winner if winner
  return variants.first if options[:exclude]

  participants = FieldTest::Participant.standardize(participants)
  membership = membership_for(participants) || FieldTest::Membership.new(experiment: id)

  if options[:variant] && variants.include?(options[:variant])
    membership.variant = options[:variant]
  else
    membership.variant ||= variants.sample
  end

  # upgrade to preferred participant
  membership.participant = participants.first

  if membership.changed?
    begin
      membership.save!
    rescue ActiveRecord::RecordNotUnique
      membership = memberships.find_by(participant: participants.first)
    end
  end

  membership.try(:variant) || variants.first
end