Class: Continuance::Durations

Inherits:
Object
  • Object
show all
Defined in:
lib/continuance/durations.rb

Overview

Durations takes a collection of duration objects on which some standard collection operations can be performed such as average etc

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(items = []) ⇒ Durations

Constructor can take a sequence of duration objects, objects outside of durations are ignored



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# File 'lib/continuance/durations.rb', line 10

def initialize(items = [])
  @items = items
end

Instance Attribute Details

#items ⇒ Object (readonly)

Returns the value of attribute items.



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# File 'lib/continuance/durations.rb', line 6

def items
  @items
end

Instance Method Details

#average ⇒ Object Also known as: arithmetic_mean, median

Given a series of durations, this function calculates the average duration by converting each duration to an absolute float value



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# File 'lib/continuance/durations.rb', line 16

def average
  time = Time.at(avg_as_f).utc.strftime('%H:%M:%S:%N')
  Duration.create(time, '%H:%M:%S:%L')
end

#max ⇒ Object

Tells us what the largest duration is of the given ones



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# File 'lib/continuance/durations.rb', line 39

def max
  items.map(&:to_f).max
end

#min ⇒ Object

Tells us what the smallest duration is of the given ones



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# File 'lib/continuance/durations.rb', line 34

def min
  items.map(&:to_f).min
end

#standard_deviation ⇒ Object

The standard deviation is simply the square root of the variance



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# File 'lib/continuance/durations.rb', line 56

def standard_deviation
  Math.sqrt(variance)
end

#total ⇒ Object

Provides a sum of all the durations



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# File 'lib/continuance/durations.rb', line 27

def total
  items.inject(0.0) do |sum, duration|
    sum += duration.to_f if duration.respond_to?(:to_f)
  end
end

#variance ⇒ Object

TODO: Add a variance and standard deviation methods to this class



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# File 'lib/continuance/durations.rb', line 44

def variance
  if items.empty?
    0
  else
    mean = average # Cache the average for future use
    diffs = items.map { |duration| duration.to_f - mean.to_f }
    diff_squares = diffs.map { |diff| diff**2 }
    diff_squares.inject(:+) / items.size
  end
end