Minimal line algebra functions in Clojure

linear-algebra.clj

(require '[clojure.core.match :refer [match]])

;; (add [[7 3] [-1 2]] [[4 2] [3 -1]]) ;; => [[11 5] [[2 1]]]

(defn add [lhs rhs]
  (match [lhs rhs]
    [(l :guard number?) (r :guard number?)] (+ lhs rhs)
    [(l :guard vector?) (r :guard vector?)] (vec (map add lhs rhs))))

;; (transpose [[5 2] [6 3] [-2 0]]) ;; => [[5 6 -2] [2 3 0]]

(defn transpose [x]
  (-> (partial map vector) (apply x) vec))

;; (product [[1 2 -3] [2 7 1]] [[5 2] [6 3] [-2 0]]) ;; => [[23 8] [50 25]]

(defn product [lhs rhs]
  (vec (for [x lhs]
         (vec (for [y (transpose rhs)]
                (reduce + (map * x y)))))))

;; (mul 3 [[11 5] [2 1]]) ;;=> [[33 15] [6 3]]

(defn mul [scalar x]
  (match [x]
    [(l :guard number?)] (* scalar l)
    [(l :guard vector?)] (vec (map #(mul scalar %1) l))))

;; (mean [10, 13, 8, 15, 8]) => 10.5

(defn mean [x]
  (float (/ (reduce + x) (count x))))

;; (variance [10, 13, 8, 15, 8]) => 7.76

(defn variance [x]
  (let [m (mean x)]
    (mean (map #(Math/pow (- %1 m) 2) x))))

;; (standard-deviation [10, 13, 8, 15, 8]) => 2.785

(defn standard-deviation [x]
  (Math/sqrt (variance x)))