← All drillsBuild a Recommender from Scratch
What you'll be able to do- ✓Build a recommender from scratch — similarity, collaborative filtering, and matrix factorization over a real ratings dataset
- ✓Represent sparse interaction data honestly, so a rating that was never given is never treated as a rating of zero
- ✓Split ratings by time and measure how much a random split flatters your results
- ✓Establish baselines before modelling, so you always know what beating nothing looks like
- ✓Measure recommendations with Recall@K, NDCG@K, MAP and catalog coverage instead of rating error alone
- ✓Train matrix factorization by gradient descent over observed entries, the way the Netflix Prize was won
- ✓Show why the best rating predictor is not the best recommender, using your own measurements
Build the system behind every "recommended for you" row you have ever seen — and, more importantly, the evaluation harness that tells you honestly whether it works, which is the part most tutorials skip and most production teams get wrong.
⌁ Amazon's item-to-item recommendations, the Netflix Prize solutions, and Spotify's early collaborative filtering all run on the techniques you build here; every modern recommender is measured against exactly these baselines.
Start this internshipCreate an account to unlock the 13 sections, the workbench, and AskThili.
BeginSections
1. Build a Recommender from Scratch
🔒 locked2. The Recommendation Problem
🔒 locked3. MovieLens, Represented Honestly
🔒 locked4. Similarity on Implicit Data
🔒 locked5. Similarity on Explicit Data
🔒 locked6. Splitting by Time
🔒 locked7. Baselines First
🔒 locked8. User-Based Collaborative Filtering
🔒 locked9. Item-Based Collaborative Filtering
🔒 locked10. How Recommendations Are Actually Judged
🔒 locked11. Matrix Factorization
🔒 locked12. Bias, Done Right
🔒 locked13. What Breaks Next
🔒 lockedDig deeper
📄Item-Based Collaborative Filtering Recommendation Algorithms (Sarwar, Karypis, Konstan & Riedl, 2001, WWW)
paper📄Matrix Factorization Techniques for Recommender Systems (Koren, Bell & Volinsky, 2009, IEEE Computer)
paper📄Amazon.com Recommendations: Item-to-Item Collaborative Filtering (Linden, Smith & York, 2003, IEEE Internet Computing)
paper📄Collaborative Filtering for Implicit Feedback Datasets (Hu, Koren & Volinsky, 2008, ICDM)
paper📄The MovieLens Datasets: History and Context (Harper & Konstan, 2015, ACM TiiS)
paper🔗thili-ai/thilirec — reference implementation
code