Exemplo n.º 1
0
  @Override
  protected void calculate(Dataset dataSet) {

    int nUsers = dataSet.getUserCount();

    similarityValues = new double[nUsers][nUsers];

    // if we want to use mapping from userId to index then generate
    // index for every userId
    if (useObjIdToIndexMapping) {
      for (User u : dataSet.getUsers()) {
        idMapping.getIndex(String.valueOf(u.getId()));
      }
    }

    for (int u = 0; u < nUsers; u++) {

      int userAId = getObjIdFromIndex(u);
      User userA = dataSet.getUser(userAId);

      for (int v = u; v < nUsers; v++) {
        int userBId = getObjIdFromIndex(v);
        User userB = dataSet.getUser(userBId);

        /* Collect shared ratings */
        Integer[] sharedItemIds = User.getSharedItems(userA, userB);

        if (sharedItemIds.length > 0) {
          double[] ratingsA = userA.getRatingsForItemList(sharedItemIds);
          double[] ratingsB = userB.getRatingsForItemList(sharedItemIds);

          /* Center ratings by subtracting average */
          double avgA = userA.getAverageRating();
          double avgB = userB.getAverageRating();
          for (int i = 0; i < sharedItemIds.length; i++) {
            ratingsA[i] = ratingsA[i] - avgA;
            ratingsB[i] = ratingsB[i] - avgB;
          }

          /* Calculate similarity - Pearson Correlation */
          PearsonCorrelation pr = new PearsonCorrelation(ratingsA, ratingsB);

          similarityValues[u][v] = pr.calculate();
        } else {
          similarityValues[u][v] = 0.0;
        }
      }
    }
  }
Exemplo n.º 2
0
 public MovieLensUserSimilarity(String id, Dataset ds) {
   this.id = id;
   this.useObjIdToIndexMapping = ds.isIdMappingRequired();
   calculate(ds);
 }