Michael D. Ekstrand

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Recommender systems are an important part of the information and e-commerce ecosystem. They represent a powerful method for enabling users to filter through large information and product spaces. Nearly two decades of research on collaborative filtering have led to a varied set of algorithms and a rich collection of tools for evaluating their performance.(More)
Recommender systems research is being slowed by the difficulty of replicating and comparing research results. Published research uses various experimental methodologies and metrics that are difficult to compare. It also often fails to sufficiently document the details of proposed algorithms or the evaluations employed. Researchers waste time reimplementing(More)
All new researchers face the daunting task of familiarizing themselves with the existing body of research literature in their respective fields. Recommender algorithms could aid in preparing these lists, but most current algorithms do not understand how to rate the importance of a paper within the literature, which might limit their effectiveness in this(More)
Recent developments in user evaluation of recommender systems have brought forth powerful new tools for understanding what makes recommendations effective and useful. We apply these methods to understand how users evaluate recommendation lists for the purpose of selecting an algorithm for finding movies. This paper reports on an experiment in which we asked(More)
Hybrid recommender systems --- systems using multiple algorithms together to improve recommendation quality --- have been well-known for many years and have shown good performance in recent demonstrations such as the NetFlix Prize. Modern hybridization techniques, such as feature-weighted linear stacking, take advantage of the hypothesis that the relative(More)
Wiki systems typically display article history as a linear sequence of revisions in chronological order. This representation hides deeper relationships among the revisions, such as which earlier revision provided most of the content for a later revision, or when a revision effectively reverses the changes made by a prior revision. These relationships are(More)
Users of complex software applications frequently need to consult documentation, tutorials, and support resources to learn how to use the software and further their understand-ing of its capabilities. Existing online help systems provide limited context awareness through "what's this?" and simi-lar techniques. We examine the possibility of making more use(More)
Most recommender systems assume user ratings accurately represent user preferences. However, prior research shows that user ratings are imperfect and noisy. Moreover, this noise limits the measurable predictive power of any recommender system. We propose an information theoretic framework for quantifying the preference information contained in ratings and(More)
LensKit is a new recommender systems toolkit aiming to be a platform for recommender research and education. It provides a common API for recommender systems, modular implementations of several collaborative filtering algorithms, and an evaluation framework for consistent, reproducible offline evaluation of recommender algorithms. In this demo, we will(More)
In the fall of 2013, we offered an open online Introduction to Recommender Systems through Coursera, while simultaneously offering a for-credit version of the course on-campus using the Coursera platform and a flipped classroom instruction model. As the goal of offering this course was to experiment with this type of instruction, we performed extensive(More)