class MoreMath::LinearRegression

def r2
  image_seq = MoreMath::Sequence.new(@image)
  sum_res   = residuals.inject(0.0) { |s, r| s + r ** 2 }
  [
    1.0 -  sum_res / image_seq.sum_of_squares,
    0.0,
  ].max
end