11 lines
317 B
Ruby
11 lines
317 B
Ruby
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module SimpleStats
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def variance(items, type = :population)
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return 0 if items.size < 2
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divisor = type == :population ? items.length : items.length - 1
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mean = items.sum / items.length.to_f
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sum = items.map{ |item| (item - mean) ** 2 }.sum
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(sum / divisor).to_f
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end
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module_function :variance
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end
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