module DescriptiveStatistics::CentralTendency

Public Instance Methods

mean() click to toggle source
# File lib/descriptive-statistics/central-tendency.rb, line 11
def mean
  return if length < 1
  sum / length.to_f
end
median() click to toggle source
# File lib/descriptive-statistics/central-tendency.rb, line 16
def median
  return if length < 1
  sorted = self.sort

  if length % 2 == 0
    (sorted[(length/2) -1 ] + sorted[length / 2]) / 2.0
  else
    sorted[length / 2]
  end
end
mode() click to toggle source
# File lib/descriptive-statistics/central-tendency.rb, line 27
def mode
  return if length < 1
  frequency_distribution = inject(Hash.new(0)) { |hash, value| hash[value] += 1; hash }
  top_2 = frequency_distribution.sort { |a,b| b[1] <=> a[1] } .take(2)
  if top_2.length == 1
    top_2.first.first # Only one value in distribution, so it's the mode.
  elsif top_2.first.last == top_2.last.last
    nil # Equal frequency, no mode.
  else
    top_2.first.first # Most frequent is mode.
  end
end
sum(identity = 0, &block) click to toggle source
# File lib/descriptive-statistics/central-tendency.rb, line 3
def sum(identity = 0, &block)
  if block_given?
    DescriptiveStatistics::Stats.new(map(&block)).sum(identity)
  else
    inject(:+) || identity
  end
end