package com.rapidminer.operator.RatingPrediction;
import java.util.ArrayList;
import java.util.List;
import com.rapidminer.correlation.Pearson;
import com.rapidminer.data.SparseMatrix;
import com.rapidminer.data.SparseMatrix_d;
import com.rapidminer.tools.container.Tupel;
/**
Copyright (C) 2010, 2011 Zeno Gantner
*This file is originally part of MyMediaLite.
*Ported by Matej Mihelcic (Ru�er Bo�kovi� Institute) 27.07.2011
*/
public class ItemKnnPearson extends _itemKnn
{
static final long serialVersionUID=3453434;
/// <summary>shrinkage (regularization) parameter</summary>
public float GetShrinkage() {
return shrinkage; }
public void SetShrinkage(float value){
shrinkage = value; }
private float shrinkage = 10;
///
public ItemKnnPearson(){super(); }
///
public void Train()
{
super.Train();
this.correlation = Pearson.Create(ratings, 1, GetShrinkage());
}
///
protected void RetrainItem(int item_id)
{
}
public void RetrainItems(List<Integer> items){
super.RetrainItems(items);
ArrayList<ArrayList<Integer>> ratings_by_other_entity = ratings.ByItem();
SparseMatrix freqs = new SparseMatrix(this.correlation.Getnum_entities(), this.correlation.Getnum_entities());
SparseMatrix_d i_sums = new SparseMatrix_d(this.correlation.Getnum_entities(), this.correlation.Getnum_entities());
SparseMatrix_d j_sums = new SparseMatrix_d(this.correlation.Getnum_entities(), this.correlation.Getnum_entities());
SparseMatrix_d ij_sums = new SparseMatrix_d(this.correlation.Getnum_entities(), this.correlation.Getnum_entities());
SparseMatrix_d ii_sums = new SparseMatrix_d(this.correlation.Getnum_entities(), this.correlation.Getnum_entities());
SparseMatrix_d jj_sums = new SparseMatrix_d(this.correlation.Getnum_entities(), this.correlation.Getnum_entities());
for(int i1=0;i1<items.size();i1++){
ArrayList<Integer> other_entity_ratings = ratings_by_other_entity.get(items.get(i1));
for (int i = 0; i < other_entity_ratings.size(); i++)
{
Integer index1 = other_entity_ratings.get(i);
int x = ratings.GetItems().get(index1);
// update pairwise scalar product and frequency
for (int j = i + 1; j < other_entity_ratings.size(); j++)
{
Integer index2 = other_entity_ratings.get(j);
int y = ratings.GetItems().get(index2);
double rating1 = ratings.GetValues(index1);
double rating2 = ratings.GetValues(index2);
// update sums
if (x < y)
{
freqs.setLocation(x, y, freqs.getLocation1(x, y)+1);
i_sums.setLocation(x, y,i_sums.getLocation1(x, y)+rating1);
j_sums.setLocation(x, y, j_sums.getLocation1(x, y)+rating2);
ij_sums.setLocation(x, y,ij_sums.getLocation1(x, y)+rating1*rating2);
ii_sums.setLocation(x, y, ii_sums.getLocation1(x, y)+rating1*rating1);
jj_sums.setLocation(x, y, jj_sums.getLocation1(x, y)+rating2*rating2);
}
else
{
freqs.setLocation(y, x, freqs.getLocation1(y, x)+1);
i_sums.setLocation(y, x, i_sums.getLocation1(y, x)+rating1);
j_sums.setLocation(y, x, j_sums.getLocation1(y, x)+rating2);
ij_sums.setLocation(y, x, ij_sums.getLocation1(y, x)+rating1*rating2);
ii_sums.setLocation(y, x, ii_sums.getLocation1(y, x)+rating1*rating1);
jj_sums.setLocation(y, x, jj_sums.getLocation1(y, x)+rating2*rating2);
}
}
}
}
List<Tupel<Integer,Integer>> elementi=freqs.NonEmptyEntryIDs();
// fill the entries with interactions
for (int i1=0;i1<elementi.size();i1++)
{
Tupel<Integer,Integer> par=elementi.get(i1);
int i=par.getFirst();
int j=par.getSecond();
int n = freqs.getLocation(i, j);
if (n < 2)
{
continue;
}
double numerator = ij_sums.getLocation(i, j) * n - i_sums.getLocation(i, j) * j_sums.getLocation(i, j);
double denominator = Math.sqrt( (n * ii_sums.getLocation(i, j) - i_sums.getLocation(i, j) * i_sums.getLocation(i, j)) * (n * jj_sums.getLocation(i, j) - j_sums.getLocation(i, j) * j_sums.getLocation(i, j)) );
if (denominator == 0)
{
continue;
}
double pmcc = numerator / denominator;
this.correlation.setLocation(i, j, this.correlation.getLocation(i, j)+(float) (pmcc * (n / (n + shrinkage))));
}
}
///
public String ToString()
{
return String.format("ItemKNNPearson k={0} shrinkage={1} reg_u={2} reg_i={3}",
K == Integer.MAX_VALUE ? "inf" : K, GetShrinkage(), RegU, RegI);
}
public void setSchrinkage(float value){
this.shrinkage=value;
}
public float getSchrinkage(){
return this.shrinkage;
}
}