Feature hashing is a powerful technique for handling high-dimensional features in machine learning. It is fast, simple, memory-efficient, and well suited to online learning scenarios. While an approximation, it has surprisingly low accuracy tradeoffs in many machine learning problems. Feature hashing has been made somewhat popular by libraries such as Vowpal Wabbit and scikit-learn. In Spark MLlib, it is mostly used for text features; however, its use cases extend more broadly. Many Spark users are not familiar with the ways in which feature hashing might be applied to their problems. In this talk, I will cover the basics of feature hashing, and how to use it for all feature types in machine learning. I will also introduce a more flexible and powerful feature hashing transformer for use within Spark ML pipelines. Finally, I will explore the performance and scalability tradeoffs of feature hashing on various datasets.
Session hashtag: #EUds15