school/coursera-recommender-systems
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fix

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This commit is contained in:
Michael Zhang 2021-09-07 14:52:45 -05:00
parent fb31f850e7
commit ed23bb6b83
Signed by: michael
GPG key ID: BDA47A31A3C8EE6B
3 changed files with 36 additions and 3 deletions
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3
nonpers-assignment/src/main/java/org/lenskit/mooc/nonpers/assoc/AssociationItemBasedItemRecommender.java
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@ -5,7 +5,6 @@ import org.lenskit.api.Result;
import org.lenskit.api.ResultList;
import org.lenskit.basic.AbstractItemBasedItemRecommender;
import org.lenskit.results.Results;
import org.lenskit.results.BasicResult;
import org.lenskit.util.collections.LongUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
@ -91,7 +90,7 @@ public class AssociationItemBasedItemRecommender extends AbstractItemBasedItemRe
Score entry = scoring.poll();
if (entry == null) break;
results.add(new BasicResult(entry.id, entry.score));
results.add(Results.create(entry.id, entry.score));
}
return Results.newResultList(results);

11
nonpers-assignment/src/main/java/org/lenskit/mooc/nonpers/assoc/LiftAssociationModelProvider.java
View file

@ -14,6 +14,7 @@ import org.slf4j.LoggerFactory;
import javax.inject.Inject;
import javax.inject.Provider;
import java.util.List;
import java.util.HashSet;
/**
* Build an association rule model using a lift metric.
@ -68,11 +69,21 @@ public class LiftAssociationModelProvider implements Provider<AssociationModel>
for (Long2ObjectMap.Entry<LongSortedSet> xEntry: itemUsers.long2ObjectEntrySet()) {
long xId = xEntry.getLongKey();
LongSortedSet xUsers = xEntry.getValue();
HashSet xSet = new HashSet(xUsers);
// set up a map to hold the scores for each 'y' item
Long2DoubleMap itemScores = new Long2DoubleOpenHashMap();
// TODO Compute lift association formulas for all other 'Y' items with respect to this 'X'
for (Long2ObjectMap.Entry<LongSortedSet> yEntry: itemUsers.long2ObjectEntrySet()) {
long yId = yEntry.getLongKey();
LongSortedSet yUsers = yEntry.getValue();
HashSet ySet = new HashSet(yUsers);
ySet.retainAll(xSet);
double p = 1.0 * ySet.size() * allUsers.size() / (xUsers.size() * yUsers.size());
itemScores.put(yId, p);
}
// save the score map to the main map
assocMatrix.put(xId, itemScores);

25
nonpers-assignment/src/main/java/org/lenskit/mooc/nonpers/mean/MeanItemBasedItemRecommender.java
View file

@ -15,6 +15,7 @@ import javax.inject.Inject;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.PriorityQueue;
/**
* An item scorer that scores each item with its mean rating.
@ -85,7 +86,29 @@ public class MeanItemBasedItemRecommender extends AbstractItemBasedItemRecommend
private ResultList recommendItems(int n, LongSet items) {
List<Result> results = new ArrayList<>();
// TODO Find the top N items by mean rating
class Score implements Comparable<Score> {
private double score;
private long id;
public Score(double score, long id) { this.score = score; this.id = id; }
@Override
public int compareTo(Score other) {
return new Double(-this.score).compareTo(new Double(-other.score));
}
}
PriorityQueue<Score> scoring = new PriorityQueue();
for (long item : items) {
double score = model.getMeanRating(item);
scoring.offer(new Score(score, item));
}
for (int i = 0; i < n; ++i) {
Score entry = scoring.poll();
if (entry == null) break;
results.add(Results.create(entry.id, entry.score));
}
return Results.newResultList(results);
}