GNU tools for data analysts: Introducing some of the GNU utilities in a Unix terminal by way of analogies to the verbs of SQL, dplyr, etc.
Branch and bound using lazily evaluated lists: Implementing a branch-and-bound solver for the knapsack problem using lazily evaluated lists, and comparing performance of different approximation algorithms.
Grouping Stack Overflow question tags: Thinking of database tables as sparse matrices allows us to do big matrix multiplications without access to much memory. One use case is to group large numbers of user-generated tags.
Creating dot-density plots: Using census demographic data to create dot-density plots of educational attainment in Alameda County.