I am working on collaborative filtering which has implemented jaccard index in it.
I have managed to get it working for user-user:
MATCH (c1:user)-[r]->(u:user)<-[r]-(c2:user)
WHERE c1 <> c2 AND c1.UserId = {UserId}
AND not (c1)-[r]->(c2)
WITH c1, c2, COUNT(DISTINCT u) as intersection
MATCH (c:user)-[r]->(u:user)
WHERE c in [c1, c2]
WITH c1, c2, intersection, COUNT(DISTINCT u) as union
// compute Jaccard index
WITH c1, c2, intersection, union, (intersection * 1.0 / union) as jaccard_index
ORDER BY jaccard_index DESC, c2.UserId
WITH c1, COLLECT([c2.UserId, jaccard_index, intersection, union])[0..{k}] as neighbors
WHERE SIZE(neighbors) = {k} // return users with enough neighbors
RETURN c1.UserId, neighbors```
But the problem is that when I want to change slightly this algorithm so it recommends an activity that most similar user to me has been involved: user-activity somehow its not working.
this is what I have now:
MATCH (u1:user),(u:user)-[r]->(a:activity)
WHERE u1.UserId = {UserId}
AND (u)-[r]->(a)
AND not (u1)-[r]->(a)
WITH u1, a, COUNT(DISTINCT u) as cnt
ORDER BY u1.UserId, cnt DESC
RETURN u1.UserId as user, COLLECT([a._bldrId, cnt])[0..{n}] as recos , COLLECT([a.Title,cnt])[0..{n}] as recos_names
```
It works, but I'm struggling to implement jaccard index here.
Could anybody help with it ?
