Module: Riveter::CoreExtensions::ArrayExtensions

Extended by:
ActiveSupport::Concern
Included in:
Array
Defined in:
lib/riveter/core_extensions.rb

Instance Method Summary collapse

Instance Method Details

#average ⇒ Object

average of a set of numbers



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# File 'lib/riveter/core_extensions.rb', line 57

def average
  self.sum / self.length.to_f
end

#cumulative_sum ⇒ Object 



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# File 'lib/riveter/core_extensions.rb', line 38

def cumulative_sum
  sum = 0
  self.map {|x| sum += x}
end

#find_each_with_order(&block) ⇒ Object Also known as: find_each

make compatible with an ActiveRelation



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# File 'lib/riveter/core_extensions.rb', line 93

def find_each_with_order(&block)
  self.each(&block) if block_given?
end

#nil_sum(identity = nil, &block) ⇒ Object

pure genious



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# File 'lib/riveter/core_extensions.rb', line 44

def nil_sum(identity = nil, &block)
  if block_given?
    self.inject(identity) {|sum, x|
      ((sum || 0) + (yield(x) || 0)) || sum
    }
  else
    self.inject(identity) {|sum, x|
      ((sum || 0) + (x || 0)) || sum
    }
  end
end

#round(places) ⇒ Object

rounds each items to the specified number of places



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# File 'lib/riveter/core_extensions.rb', line 88

def round(places)
  self.collect {|x| x.round(places) }
end

#standard_deviation ⇒ Object

standard deviation of an array of numbers



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# File 'lib/riveter/core_extensions.rb', line 68

def standard_deviation
  Math.sqrt(self.variance)
end

#to_hash_for(&block) ⇒ Object

returns a hash of the items, indexed by the given items attribute



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# File 'lib/riveter/core_extensions.rb', line 73

def to_hash_for(&block)
  if block_given?
    self.inject({}) do |hash, record|
      hash[yield(record)] = record
      hash
    end
  else
    self.inject({}) do |hash, record|
      hash[record] = record
      hash
    end
  end
end

#variance ⇒ Object

variance of a set of numbers



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# File 'lib/riveter/core_extensions.rb', line 62

def variance
  avg = self.average
  self.inject(0.0) {|acc, value| acc + ((value - avg)**2) } / (self.length.to_f - 1)
end