Module: Measurable::Maxmin

Included in:
Measurable
Defined in:
lib/measurable/maxmin.rb

Instance Method Summary collapse

Instance Method Details

#maxmin(u, v) ⇒ Object

call-seq:

maxmin(u, v) -> Float

The “Max-min distance” is used to measure similarity between two vectors.

When used in k-means clustering, this similarity measure can give better results in some datasets, as pointed out in the paper “K-means clustering using Max-min distance measure” — Visalakshi, N. K.; Suguna, J.

See: ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=05156398

Arguments:

  • u -> An array of Numeric objects.

  • v -> An array of Numeric objects.

Returns:

  • Similarity between u and v.

Raises:

  • ArgumentError -> The sizes of u and v don’t match.

Raises:

  • (ArgumentError) 


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# File 'lib/measurable/maxmin.rb', line 22

def maxmin(u, v)
  # TODO: Change this to a more specific, custom-made exception.
  raise ArgumentError if u.size != v.size

  sum_min, sum_max = u.zip(v).reduce([0.0, 0.0]) do |acc, attributes|
    acc[0] += attributes.min
    acc[1] += attributes.max
    acc
  end

  sum_min / sum_max
end