AI engineering glossary · Time series recsys
What is user-item matrix?
User-item matrix (also called Interaction matrix, Rating matrix): A table with users as rows, items as columns and each cell holding a rating, click, purchase or blank. It is usually extremely sparse because most users interact with a tiny fraction of items.
User-item matrix: an example
1 million users and 100,000 items give 10^11 cells, of which perhaps 50 million are filled.
Related terms
More Time series recsys terms
- Vector autoregression
- Volatility clustering
- Weak stationarity
- Weighted absolute percentage error
- White noise
- Wide and Deep
- Additive decomposition
- Alternating least squares
Where you learn it
User-item matrix is part of the AI Engineering Program, which teaches it with notes, a hands-on lab and an exam. The first lesson is free.