Implements 3 types of normalization in ruby

normalization.rb

class Array
  # Few types of normalizations
  # https://developers.google.com/machine-learning/data-prep/transform/normalization

  def normalize
    return if self.empty?

    x_min, x_max = self.minmax
    dx = (x_max-x_min).to_f

    self.map { ((_1 - x_min) / dx) * 100 }
  end

  def mean_normalize
    return if self.empty?

    mean = self.reduce(&:+) / self.count

    self.map { _1 / mean }
  end

  def clipping_normalize(max = nil)
    max ||= self.max
    self.map { _1 > max ? max : _1  }.normalize
  end
  
  # not a normalization but I find it useful
  def geometric_mean
    return if self.empty?
    
    self.reduce(&:*) ** (1.0 / self.count)
  end
end

# usage ex:
[1,2,3].normalize
# => [0.0, 50.0, 100.0]

# x can't be greater than 2
[1,2,3].clipping_normalize(2)
# => [0.0, 100.0, 100.0]