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An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Users’ ratings are vectors; similar taste means similar directions.
• Centre ratings first; the cosine then becomes a correlation.
• Predict ratings as similarity-weighted averages of similar users.

Steps

1. Ratings as vectors
2. Cosine similarity
3. Centring the ratings
4. Your taste twin
5. Predict the rating
6. The cold start