arvanasse

normalize = lambda{|ary| mean = ary.sum/ary.length.to_f; ary.map{|x| x-mean}}

normalized_xs = normalize.call(xs)
normalized_ys = normalize.call(ys)

beta_hat = normalized_xs.zip(normalized_ys).map {|x, y| x*y }.sum / normalized_xs.inject(0) {|sum, x| sum + x*x }
alpha_hat = y_bar - beta_hat * x_bar

[[0, alpha_hat], [xs.last, (alpha_hat + xs.last * beta_hat)]]