Reductio is a library for generating Crossfilter reduce functions and applying them to Crossfilter groups. Crossfilter supports basic count and sum aggregations, but even aggregations as conceptually simple as a group minimum or maximum can be difficult to build correctly and efficiently on a Crossfilter group. Reductio provides helper functions that generate these aggregations in an efficient and composable way, making it easy to use more complex aggregations with Crossfilter and to have more than one aggregation per group without having to worry about designing 2-way reduce functions. If something doesn't appear to be working or you're having trouble with implementing something, it will usually be best to ask a question on Stackoverflow and tag the question with the reductio tag. When you ask your question, it is best to put together a working example showing the problem you are having. A JSFiddle template is available that already includes the Reductio and Crossfilter libraries, as well as dc.js. Use that template to make an example showing what you are seeing. In your question, reference the example, explain what you are seeing, and explain what you expect or want to see instead.