Class: Array

Inherits:
Object
  • Object
show all
Defined in:
lib/overloads/array.rb

Instance Method Summary collapse

Instance Method Details

#merge_hashes_using_key(key) ⇒ Object

For reference: stackoverflow.com/questions/27249327/how-to-merge-hashes-if-a-specified-keys-values-are-same-in-a-array Credits to stackoverflow.com/users/390819/w0lf for the solution



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# File 'lib/overloads/array.rb', line 26

def merge_hashes_using_key(key)
  return false unless self.length > 0

  arr = self

  arr.group_by{ |h| h[key] }.collect{ |_, hs| hs.reduce(:merge) }
end

#stdevp ⇒ Object

For reference: www.mathsisfun.com/data/standard-deviation-formulas.html Population standard deviation



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# File 'lib/overloads/array.rb', line 5

def stdevp
  return false unless self.length > 0
  arr = self
  # Step 1: Get the mean
  mean = arr.inject(:+).to_f / arr.length.to_f

  # Step 2: Subtract the mean and square the result
  step_2 = arr.reduce([]) do |i, n|
    i << (n.to_f - mean) ** 2
  end

  # Step 3: Get mean of step 2
  step_3 = step_2.inject(:+).to_f / step_2.length.to_f

  # Step 4: Square root of step 3
  Math.sqrt(step_3).to_f
end