Class: Metrics::Instruments::Histogram

Inherits:
Instrument
  • Object
show all
Defined in:
lib/ruby-metrics/instruments/histogram.rb

Direct Known Subclasses

ExponentialHistogram, UniformHistogram

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from Instrument

#tag, #tags

Constructor Details

#initialize(type = :uniform) ⇒ Histogram

Returns a new instance of Histogram.



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 10

def initialize(type = :uniform)
  @sample =
    case type
    when :uniform
      Metrics::Statistics::UniformSample.new
    when :exponential
      Metrics::Statistics::ExponentialSample.new
    else
      raise ArgumentError, "Unknown type #{type.inspect}"
    end

  clear
end

Instance Attribute Details

#count ⇒ Object (readonly)

Returns the value of attribute count.



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 8

def count
  @count
end

Instance Method Details

#as_json(*_) ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 125

def as_json(*_)
  {
    :min         => min,
    :max         => max,
    :mean        => mean,
    :variance    => variance,
    :percentiles => quantiles(Timer::DEFAULT_PERCENTILES)
  }
end

#clear ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 33

def clear
  @sample.clear
  @min = nil
  @max = nil
  @sum = 0
  @count = 0
  @variance_m = -1
  @variance_s = 0
end

#max ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 97

def max
  @max || 0.0
end

#mean ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 105

def mean
  if @count > 0
    @sum / @count
  else
    0.0
  end
end

#min ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 101

def min
  @min || 0.0
end

#quantiles(percentiles) ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 43

def quantiles(percentiles)
  # Calculated using the same logic as R and Excel use
  # as outlined by the NIST here: http://www.itl.nist.gov/div898/handbook/prc/section2/prc252.htm

  sorted_values = @sample.values[0...@count].sort
  scores = { }
  percentiles.each do |pct|
    scores[pct] =
      if @count == 0
        0.0
      else
        index = pct * (sorted_values.length - 1) + 1.0
        if index <= 1
          sorted_values.first
        elsif index >= sorted_values.length
          sorted_values.last
        else
          lower = sorted_values[index.to_i - 1]
          upper = sorted_values[index.to_i]
          lower + (index - index.floor) * (upper - lower)
        end
    end
  end
  scores
end

#std_dev ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 113

def std_dev
  if @count > 0
    Math.sqrt(variance)
  else
    0.0
  end
end

#to_json(*_) ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 135

def to_json(*_)
  as_json.to_json
end

#update(value) ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 24

def update(value)
	@count += 1
	@sum += value
	@sample.update(value)
	update_max(value)
	update_min(value)
  update_variance(value)
end

#update_max(value) ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 75

def update_max(value)
  if @max.nil? || value > @max
    @max = value
  end
end

#update_min(value) ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 69

def update_min(value)
  if @min.nil? || value < @min
    @min = value
  end
end

#update_variance(value) ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 81

def update_variance(value)
  new_m = @variance_m + ((value - @variance_m) / @count)
  new_s = @variance_s + ((value - @variance_m) * (value - new_m))

  @variance_m = new_m
  @variance_s = new_s
end

#values ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 121

def values
  @sample.values
end

#variance ⇒ Object 



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# File 'lib/ruby-metrics/instruments/histogram.rb', line 89

def variance
  if @count <= 1
    0.0
  else
    @variance_s.to_f / (@count - 1)
  end
end