71 lines
1.3 KiB
Crystal
71 lines
1.3 KiB
Crystal
# There are several methods for computing the quartiles of an array.
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#
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# This library utilizes the method proposed by John Tukey
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# https://en.wikipedia.org/wiki/Quartile#Method_2
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#
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module Math::Quartile
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def lower_quartile : Float64
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return 0.0_f64 if empty?
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m = self.median
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lower_half = self.select { |i| i <= m }
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lower_half.median
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end
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# alias
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def first_quartile : Float64
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lower_quartile
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end
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# alias
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def second_quartile : Float64
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median
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end
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def upper_quartile : Float64
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return 0.0_f64 if empty?
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m = self.median
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upper_half = self.select { |i| i >= m }
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upper_half.median
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end
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# alias
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def third_quartile : Float64
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upper_quartile
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end
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def quartiles : Array(Float64)
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[first_quartile, second_quartile, third_quartile]
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end
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def iqr : Float64
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third_quartile - first_quartile
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end
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# alias
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def interquartile_range : Float64
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iqr
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end
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def lower_fence(k : Number = 1.5) : Float64
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lower_quartile - k * iqr
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end
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def upper_fence(k : Number = 1.5) : Float64
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upper_quartile + k * iqr
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end
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def lower_outliers(k : Number = 1.5) : Array
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lf = lower_fence k
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self.select { |i| i < lf }
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end
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def upper_outliers(k : Number = 1.5) : Array
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uf = upper_fence k
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self.select { |i| i > uf }
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end
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end
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module Enumerable(T)
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include Math::Quartile
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end
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