module Enumerable

Public Instance Methods

median(*args, &block) click to toggle source
# File lib/active_median/enumerable.rb, line 3
def median(*args, &block)
  if !block && respond_to?(:scoping)
    scoping { @klass.median(*args) }
  elsif !block && respond_to?(:with_scope)
    with_scope(self) { klass.median(*args) }
  else
    raise ArgumentError, "wrong number of arguments (given #{args.size}, expected 0)" if args.any?
    percentile(0.5, &block)
  end
end
percentile(*args, &block) click to toggle source
# File lib/active_median/enumerable.rb, line 16
def percentile(*args, &block)
  if !block && respond_to?(:scoping)
    scoping { @klass.percentile(*args) }
  elsif !block && respond_to?(:with_scope)
    with_scope(self) { klass.percentile(*args) }
  else
    raise ArgumentError, "wrong number of arguments (given #{args.size}, expected 1)" if args.size != 1

    percentile = args[0].to_f
    raise ArgumentError, "percentile is not between 0 and 1" if percentile < 0 || percentile > 1

    # uses C=1 variant, like percentile_cont
    # https://en.wikipedia.org/wiki/Percentile#The_linear_interpolation_between_closest_ranks_method
    sorted = map(&block).sort
    x = percentile * (sorted.size - 1)
    r = x % 1
    i = x.floor
    if i == sorted.size - 1
      sorted[-1]
    else
      sorted[i] + r * (sorted[i + 1] - sorted[i])
    end
  end
end