gistfile1.scala

package chapter2

import scala.math._

object Recommendations {
  def sim_distance(preferences: Map[String, Map[String, Double]],
                   person1: String, person2: String)= {
    val p1=preferences(person1)
    val p2=preferences(person2)
    val si: Set[String] = p1.keySet.intersect(p2.keySet)

    if (si.isEmpty) {
      0.0
    }

    var sum:Double=0
    //sum1=si map ((k)=>pow(preferences(person1)(k) - preferences(person2)(k), 2)) reduceLeft( _ + _ )

    si foreach ((k) => sum += pow(p1(k) - p2(k), 2))
    1.0/(1.0+sum)
  }

  def main(args: Array[String]) = {
    val critics: Map[String, Map[String, Double]] =
      Map("Lisa Rose" -> Map(
        "Lady in the Water" -> 2.5,
        "Snakes on a Plane" -> 3.5,
        "Just My Luck" -> 3.0,
        "Superman Returns" -> 3.5,
        "You, Me, and Dupree" -> 2.5,
        "The Night Listener" -> 3.0
      ),
        "Gene Seymour" -> Map(
          "Lady in the Water" -> 3.0,
          "Snakes on a Plane" -> 3.5,
          "Just My Luck" -> 1.5,
          "Superman Returns" -> 5.0,
          "You, Me, and Dupree" -> 3.5,
          "The Night Listener" -> 3.0
        ),
        "Michael Phillips" -> Map(
          "Lady in the Water" -> 2.5,
          "Snakes on a Plane" -> 3.0,
          "Superman Returns" -> 3.5,
          "The Night Listener" -> 4.0
        ),
        "Claudia Puig" -> Map(
          "Snakes on a Plane" -> 3.5,
          "Just My Luck" -> 3.0,
          "Superman Returns" -> 4.0,
          "You, Me, and Dupree" -> 2.5,
          "The Night Listener" -> 4.5
        ),
        "Mick Lasalle" -> Map(
          "Lady in the Water" -> 3.0,
          "Snakes on a Plane" -> 4.0,
          "Just My Luck" -> 2.0,
          "Superman Returns" -> 3.0,
          "You, Me, and Dupree" -> 2.0,
          "The Night Listener" -> 3.0
        ),
        "Jack Matthews" -> Map(
          "Lady in the Water" -> 3.0,
          "Snakes on a Plane" -> 4.0,
          "Superman Returns" -> 5.0,
          "You, Me, and Dupree" -> 3.5,
          "The Night Listener" -> 3.0
        ),
        "Toby" -> Map(
          "Snakes on a Plane" -> 4.5,
          "Superman Returns" -> 4.0,
          "You, Me, and Dupree" -> 1.0
        )
      )
    critics foreach ((t) => println(t._1 + "-->" + t._2))

    println(critics("Toby"))

    println(sim_distance(critics, "Lisa Rose", "Gene Seymour"))
  }
}