gistfile1.rb

class Array
  
# groups an array of sorted numbers
  # into clusters, where each cluster contains
  # values that are more close in value than
  # either the left or right neighboring clusters.
  def clusterize
    c = [[]]
    each_with_index do |x,i|
      # first time 'round, add the value (x)
      # to the current "cluster", then move
      # to the next value
      c[-1] << x && next if i == 0
      
      # n is the difference of the next value
      # and the current value....
      # or 0 if there isn't a next
      n = i == size-1 ? 0 : x - self[i+1]
      
      # p is the diff. of the next value
      # and the current value
      p = self[i-1] - x
      
      # add a new "cluster"...
      # if the previous diff is greater than the next diff
      c << [] if p > n
      
      # add the current value (x) to the last cluster
      c[-1] << x
    end
    c
  end

end

data = [9.537862, 9.537862, 6.579175, 3.3948307, 3.3948307, 3.2919545, 3.1890779, 3.1330175, 3.0862014, 3.0862014, 3.0862014, 3.0862014, 3.0862014, 3.0862014, 2.731317, 2.731317, 2.2361403, 2.2361403, 2.174609, 2.1746087, 1.763103, 1.7116647, 1.6579969, 1.6579969, 1.6579969, 1.6395404, 1.6395404, 1.6395404, 1.5465399, 1.4947798]

result = data.clusterize

# result =>

[[9.537862, 9.537862, 6.579175], [3.3948307, 3.3948307, 3.2919545], [3.1890779], [3.1330175], [3.0862014, 3.0862014, 3.0862014, 3.0862014, 3.0862014, 3.0862014], [2.731317, 2.731317], [2.2361403, 2.2361403], [2.174609, 2.1746087], [1.763103, 1.7116647], [1.6579969, 1.6579969, 1.6579969], [1.6395404, 1.6395404, 1.6395404], [1.5465399], [1.4947798]]