Building a Machine Learning Recommendation System
Chapter 1: Foundations of Recommendation Systems
What are Recommendation Systems?
Taxonomy of Recommender Engines
Understanding User-Item Interaction Data
Implicit vs. Explicit Feedback
The Cold-Start Problem
Preparing Your Development Environment
Practice: Loading and Inspecting a Dataset
Chapter 2: Content-Based Filtering
The Mechanics of Content-Based Recommenders
Creating Item Profiles from Metadata
Vectorizing Text Data with TF-IDF
Computing Similarity with Cosine Distance
Generating User Profiles
Producing Content-Based Recommendations
Hands-on Practical: Building a Movie Recommender
Chapter 3: Neighborhood-Based Collaborative Filtering
The Rationale Behind Collaborative Filtering
The User-Item Interaction Matrix
User-Based vs. Item-Based Approaches
Finding Similar Users and Items with k-Nearest Neighbors
Calculating Similarity Metrics
Making Predictions with Weighted Averages
Addressing Sparsity in the Interaction Matrix
Hands-on Practical: Implementing an Item-Based Filter
Chapter 4: Model-Based Collaborative Filtering with Matrix Factorization
From Neighborhoods to Latent Factor Models
Introduction to Matrix Factorization
Singular Value Decomposition (SVD) for Recommendations
Optimization with Stochastic Gradient Descent (SGD)
Regularization to Prevent Overfitting
Using Libraries for Matrix Factorization
Hands-on Practical: Generating Recommendations with SVD
Chapter 5: Evaluating Recommendation Systems
The Importance of Recommender Evaluation
Offline vs. Online Evaluation Methods
Splitting Data for Recommender Evaluation
Prediction Accuracy Metrics: RMSE and MAE
Ranking Metrics: Precision and Recall at K
Mean Average Precision (MAP)
Normalized Discounted Cumulative Gain (NDCG)
Hands-on Practical: Measuring Model Performance
Chapter 6: Constructing a Hybrid Recommendation System
Limitations of Single-Algorithm Systems
Combining Recommender Models
Weighted Hybridization
Switching and Mixed Hybridization Techniques
Feature Combination Methods
Building a System that Blends Content and Collaborative Signals
Hands-on Practical: A Weighted Hybrid Movie Recommender
Splitting Data for Recommender Evaluation
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- Recommender Systems Handbook, Francesco Ricci, Lior Rokach, Bracha Shapira (Editors), 2022 (Springer US) DOI: 10.1007/978-1-0716-2580-5 - A comprehensive reference covering all aspects of recommender systems, including detailed discussions on evaluation methodologies and the importance of appropriate data splitting strategies, particularly for handling temporal dynamics.
- On the Difficulty of Reproducing Recommendation System Evaluations, Luca Cremonesi, Luigi Dacrema, and Francesco Ricci, 2019 Proceedings of the 13th ACM Conference on Recommender Systems (RecSys '19) (ACM) DOI: 10.1145/3298689.3346995 - An important paper that examines the challenges and common pitfalls in evaluating recommender systems, emphasizing the need for robust experimental setups, including temporal data splits, to ensure reliable performance metrics.
- Applied Predictive Modeling, Max Kuhn and Kjell Johnson, 2013 (Springer) DOI: 10.1007/978-1-4614-6849-3 - This textbook provides practical guidance on building and evaluating predictive models. Chapter 10 covers data splitting strategies, including specific considerations for time series data, which forms the theoretical basis for temporal splits in recommendation systems.