Linear regression

linreg.clj

(defn reg [pairs]
  (let [M (count pairs)
        bldr (fn [acc [x y]]
               (let [x (bigdec x)
                     y (bigdec y)]
                 (merge-with
                  + acc
                  {:∑x x
                   :∑y y
                   :∑xy (* x y)
                   :∑x² (pow x 2)})))
        s (reduce bldr {} pairs)
        ∑x² (:∑x² s) ∑xy (:∑xy s) ∑x (:∑x s) ∑y  (:∑y s)
        ∑x∑y (* ∑x ∑y)
        w1 (/ (- (* M ∑xy) ∑x∑y)
              (- (* M ∑x²) (pow ∑x 2)))
        w0 (- (/ ∑y M) (/ (* w1 ∑x) M))]
    {:w1 w1 :w0 w0}))