# 7: Collaborative filtering

*recommendation systems*—algorithms which guess what products and services you might like, based on your past behavior. These systems largely rely on *collaborative-filtering*, an approach based on linear algebra that fills in the missing values in a matrix. Today we’ll see two ways to do this: one based on a classic linear algebra formulation, and one based on deep learning.

## Video

## Resources

- Notebooks for this lesson:
- Road to the top: part 3 and part 4
- Collaborative Filtering Deep Dive

- Spreadsheets for this lesson:
- Things that confused me about cross-entropy by Chris Said
- Label Smoothing Explained using Microsoft Excel by Aman Arora