These are the slides from my talk to the Bay Area Clojure Group meeting in San Francisco on June 6, 2013.
The slides are not meant to stand alone, so they may not be completely useful if you did not attend.
Here is the description of the talk sent out in advance:
Tom Faulhaber will talk about interactive data analysis focusing on data organization and the split-apply-combine pattern. You'll find that split-apply-combine is a powerful tool that applies to many of the data problems that we look at in Clojure. This pattern is the basis of the popular plyr package developed by Hadley Wickham in the R language.
Tom will demonstrate some basic ideas of data analysis and show how they're implemented in the Incanter system. We'll discuss split-apply-combine and how it's used in Incanter today. Then, we'll discuss how to implement a full version of split-apply-combine in Clojure on top of Incanter's dataset type. Finally, we'll use our implementation to learn about some real data.