incanter.contrib.vecmath.naive

naive.clj

(ns ^{:doc "Naive implementation of vector products."}
  incanter.contrib.vecmath.naive
  (:use [incanter.core :only (matrix mmult)]))

(defn dot
  "Dot product between two vectors."
  [u v]
  (apply + (map * u v)))

(defn cross
  "Cross product between two vectors.

  Implementation:
  http://en.wikipedia.org/wiki/Cross_product#Conversion_to_matrix_multiplication
  "
  [u v]
  (let [[a1 a2 a3] u
        m (matrix [[0 (- a3) a2]
                   [a3 0 (- a1)]
                   [(- a2) a1 0]])]
      (mmult m (matrix v))))