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Contents
require 'active_support/core_ext/enumerable' # For Array#sum
module MoreCoreExtensions
module ArrayMath
#
# Returns the mean of an Array of Numerics.
#
# [1, 2, 3, 4, 5].mean #=> 3.0
# [1.0, 2.0, 3.0].mean #=> 2.0
def mean
sum.to_f / length
end
#
# Returns the standard deviation of an Array of Numerics.
#
# [1, 2, 3, 4, 5].stddev #=> 1.5811388300841898
# [1.0, 2.0, 3.0].stddev #=> 1.0
def stddev
Math.sqrt(variance)
end
#
# Returns the variance of an Array of Numerics.
#
# [1, 2, 3, 4, 5].variance #=> 2.5
# [1.0, 2.0, 3.0].variance #=> 1.0
def variance
μ = mean
reduce(0) { |m, i| m + (i - μ).square } / (length - 1)
end
end
end
Array.send(:include, MoreCoreExtensions::ArrayMath)
Version data entries
14 entries across 14 versions & 1 rubygems