dtw.clj

(ns dtw.core
  (:use arcadia.core)
  (:import [UnityEngine Vector3]))

(defn distance [a b]
  (Vector3/Distance a b))

(defn dtw [s t]
  (let [n (count s)
        m (count t)
        bottom (apply hash-map
                      (mapcat (fn [i] [[i 0] Double/PositiveInfinity])
                              (range 1 n)))
        left (apply hash-map
                    (mapcat (fn [i] [[0 i] Double/PositiveInfinity])
                            (range 1 m)))
        d (merge {[0 0] 0} bottom left)] 
    ((reduce (fn [acc [i j]]
                     (let [cost (distance (nth s i)
                                          (nth t j))]
                       (assoc acc [i j] (+ cost
                                           (min (acc [(dec i) j])
                                                (acc [i (dec j)])
                                                (acc [(dec i) (dec j)]))))))
                   d
                   (for [i (range 1 n)
                         j (range 1 m)]
                     [i j]))
     [(dec n) (dec m)])))

(dtw (repeatedly 10 #(UnityEngine.Random/insideUnitSphere))
     (repeatedly 10 #(UnityEngine.Random/insideUnitSphere)))
; => 9.79245162010193

(let [s (repeatedly 20 #(UnityEngine.Random/insideUnitSphere))]
  (dtw s s))
; => 0.0