Module: Enumerable

Defined in:
lib/enumerable/standard_deviation/standard_deviation.rb

Instance Method Summary collapse

Instance Method Details

#max_standard_deviation ⇒ Object Also known as: max_std_dev 



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# File 'lib/enumerable/standard_deviation/standard_deviation.rb', line 21

def max_standard_deviation
  mean + standard_deviation
end

#mean ⇒ Object 



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# File 'lib/enumerable/standard_deviation/standard_deviation.rb', line 6

def mean
  sum / length.to_f
end

#min_standard_deviation ⇒ Object Also known as: min_std_dev 



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# File 'lib/enumerable/standard_deviation/standard_deviation.rb', line 26

def min_standard_deviation
  mean - standard_deviation
end

#sample_variance ⇒ Object 



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# File 'lib/enumerable/standard_deviation/standard_deviation.rb', line 10

def sample_variance
  m = mean
  sum = inject(0){|sum, i| sum + (i - m) ** 2 }
  sum / (length - 1).to_f
end

#standard_deviation ⇒ Object Also known as: std_dev 



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# File 'lib/enumerable/standard_deviation/standard_deviation.rb', line 16

def standard_deviation
  Math.sqrt(sample_variance)
end

#sum ⇒ Object 



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# File 'lib/enumerable/standard_deviation/standard_deviation.rb', line 2

def sum
  inject(0){|sum, i| sum + i }
end