Class: SISFC::Statistics

Inherits:
Object
  • Object
show all
Defined in:
lib/sisfc/statistics.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(opts = {}) ⇒ Statistics

see en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Online_algorithm and www.johndcook.com/blog/standard_deviation/



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# File 'lib/sisfc/statistics.rb', line 13

def initialize(opts={})
  @n    = 0 # number of requests
  @mean = 0.0
  @m_2  = 0.0
  @longer_than = init_counters_for_longer_than_stats(opts)
  @received = 0
end

Instance Attribute Details

#longer_than ⇒ Object (readonly)

Returns the value of attribute longer_than.



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# File 'lib/sisfc/statistics.rb', line 8

def longer_than
  @longer_than
end

#mean ⇒ Object (readonly)

Returns the value of attribute mean.



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# File 'lib/sisfc/statistics.rb', line 8

def mean
  @mean
end

#n ⇒ Object (readonly) Also known as: closed

Returns the value of attribute n.



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# File 'lib/sisfc/statistics.rb', line 8

def n
  @n
end

#received ⇒ Object (readonly)

Returns the value of attribute received.



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# File 'lib/sisfc/statistics.rb', line 8

def received
  @received
end

Instance Method Details

#record_request(req) ⇒ Object 



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# File 'lib/sisfc/statistics.rb', line 25

def record_request(req)
  # get new sample
  x = req.ttr
  raise "TTR #{x} for request #{req.rid} invalid!" unless x > 0.0

  @longer_than.each_key do |k|
    @longer_than[k] += 1 if x > k
  end

  # update counters
  @n += 1
  delta = x - @mean
  @mean += delta / @n
  @m_2  += delta * (x - @mean)
end

#request_received ⇒ Object 



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# File 'lib/sisfc/statistics.rb', line 21

def request_received
  @received += 1
end

#to_s ⇒ Object 



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# File 'lib/sisfc/statistics.rb', line 45

def to_s
  "received: #{@received}, closed: #{@n}, " +
  "(mean: #{@mean}, variance: #{variance}, longer_than: #{@longer_than.to_s})"
end

#variance ⇒ Object 



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# File 'lib/sisfc/statistics.rb', line 41

def variance
  @m_2 / (@n - 1)
end