Get sigma value : Math extensions « Development « Ruby

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2. Development
3. Math extensions

Get sigma value

def mean(x)
  sum=0
  x.each {|v| sum += v}
  sum/x.size
end
def variance(x)
  m = mean(x)
  sum =0.0
  x.each {|v| sum += (v-m)**2 }
  sum/x.size
end

def sigma(x)
  Math.sqrt(variance(x))
end

data = [2,3,2,2,3,4,5,5,4,3,4,1,2 ]
puts sigma(data)     # 1.20894105

 

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