--- a/marking2/danube.scala Fri Apr 26 17:29:30 2024 +0100
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,180 +0,0 @@
-// Part 2 and 3 about Movie Recommendations
-// at Danube.co.uk
-//===========================================
-
-import io.Source
-import scala.util._
-
-object CW7b { // for purposes of generating a jar
-
-// (1) Implement the function get_csv_url which takes an url-string
-// as argument and requests the corresponding file. The two urls
-// of interest are ratings_url and movies_url, which correspond
-// to CSV-files.
-// The function should ReTurn the CSV file appropriately broken
-// up into lines, and the first line should be dropped (that is without
-// the header of the CSV file). The result is a list of strings (lines
-// in the file).
-
-def get_csv_url(url: String) : List[String] = {
- val csv = Source.fromURL(url)("ISO-8859-1")
- csv.mkString.split("\n").toList.drop(1)
-}
-
-val ratings_url = """https://nms.kcl.ac.uk/christian.urban/ratings.csv"""
-val movies_url = """https://nms.kcl.ac.uk/christian.urban/movies.csv"""
-
-// test cases
-
-
-//val ratings = get_csv_url(ratings_url)
-//val movies = get_csv_url(movies_url)
-
-//ratings.length // 87313
-//movies.length // 9742
-
-// (2) Implement two functions that process the CSV files. The ratings
-// function filters out all ratings below 4 and ReTurns a list of
-// (userID, movieID) pairs. The movies function just ReTurns a list
-// of (movieId, title) pairs.
-
-
-def process_ratings(lines: List[String]) : List[(String, String)] = {
- for (cols <- lines.map(_.split(",").toList);
- if (cols(2).toFloat >= 4)) yield (cols(0), cols(1))
-}
-
-def process_movies(lines: List[String]) : List[(String, String)] = {
- for (cols <- lines.map(_.split(",").toList)) yield (cols(0), cols(1))
-}
-
-// test cases
-
-//val good_ratings = process_ratings(ratings)
-//val movie_names = process_movies(movies)
-
-//good_ratings.length //48580
-//movie_names.length // 9742
-
-//==============================================
-// Do not change anything below, unless you want
-// to submit the file for the advanced part 3!
-//==============================================
-
-
-// (3) Implement a grouping function that calulates a map
-// containing the userIds and all the corresponding recommendations
-// (list of movieIds). This should be implemented in a tail
-// recursive fashion, using a map m as accumulator. This map
-// is set to Map() at the beginning of the claculation.
-
-def groupById(ratings: List[(String, String)],
- m: Map[String, List[String]]) : Map[String, List[String]] = ratings match {
- case Nil => m
- case (id, mov) :: rest => {
- val old_ratings = m.getOrElse (id, Nil)
- val new_ratings = m + (id -> (mov :: old_ratings))
- groupById(rest, new_ratings)
- }
-}
-
-// test cases
-//val ratings_map = groupById(good_ratings, Map())
-//val movies_map = movie_names.toMap
-
-//ratings_map.get("414").get.map(movies_map.get(_)) // most prolific recommender with 1227 positive ratings
-//ratings_map.get("474").get.map(movies_map.get(_)) // second-most prolific recommender with 787 positive ratings
-//ratings_map.get("214").get.map(movies_map.get(_)) // least prolific recommender with only 1 positive rating
-
-
-
-//(4) Implement a function that takes a ratings map and a movie_name as argument.
-// The function calculates all suggestions containing
-// the movie mov in its recommendations. It ReTurns a list of all these
-// recommendations (each of them is a list and needs to have mov deleted,
-// otherwise it might happen we recommend the same movie).
-
-def favourites(m: Map[String, List[String]], mov: String) : List[List[String]] =
- (for (id <- m.keys.toList;
- if m(id).contains(mov)) yield m(id).filter(_ != mov))
-
-
-
-// test cases
-// movie ID "912" -> Casablanca (1942)
-// "858" -> Godfather
-// "260" -> Star Wars: Episode IV - A New Hope (1977)
-
-//favourites(ratings_map, "912").length // => 80
-
-// That means there are 80 users that recommend the movie with ID 912.
-// Of these 80 users, 55 gave a good rating to movie 858 and
-// 52 a good rating to movies 260, 318, 593.
-
-
-// (5) Implement a suggestions function which takes a rating
-// map and a movie_name as arguments. It calculates all the recommended
-// movies sorted according to the most frequently suggested movie(s) first.
-def suggestions(recs: Map[String, List[String]],
- mov_name: String) : List[String] = {
- val favs = favourites(recs, mov_name).flatten
- val favs_counted = favs.groupBy(identity).view.mapValues(_.size).toList
- val favs_sorted = favs_counted.sortBy(_._2).reverse
- favs_sorted.map(_._1)
-}
-
-// test cases
-
-//suggestions(ratings_map, "912")
-//suggestions(ratings_map, "912").length
-// => 4110 suggestions with List(858, 260, 318, 593, ...)
-// being the most frequently suggested movies
-
-// (6) Implement recommendations functions which generates at most
-// *two* of the most frequently suggested movies. It Returns the
-// actual movie names, not the movieIDs.
-
-def recommendations(recs: Map[String, List[String]],
- movs: Map[String, String],
- mov_name: String) : List[String] =
- suggestions(recs, mov_name).take(2).map(movs.get(_).get)
-
-
-// testcases
-
-// recommendations(ratings_map, movies_map, "912")
-// => List(Godfather, Star Wars: Episode IV - A NewHope (1977))
-
-//recommendations(ratings_map, movies_map, "260")
-// => List(Star Wars: Episode V - The Empire Strikes Back (1980),
-// Star Wars: Episode VI - Return of the Jedi (1983))
-
-// recommendations(ratings_map, movies_map, "2")
-// => List(Lion King, Jurassic Park (1993))
-
-// recommendations(ratings_map, movies_map, "0")
-// => Nil
-
-// recommendations(ratings_map, movies_map, "1")
-// => List(Shawshank Redemption, Forrest Gump (1994))
-
-// recommendations(ratings_map, movies_map, "4")
-// => Nil (there are three ratings fro this movie in ratings.csv but they are not positive)
-
-
-// If you want to calculate the recomendations for all movies.
-// Will take a few seconds calculation time.
-
-//val all = for (name <- movie_names.map(_._1)) yield {
-// recommendations(ratings_map, movies_map, name)
-//}
-
-// helper functions
-//List().take(2)
-//List(1).take(2)
-//List(1,2).take(2)
-//List(1,2,3).take(2)
-
-}
-
-