My dissertation was in mathematical logic, with no exposure to statistics or applied mathematics. As I was finishing a sabbatical in 2019, my chair told me that the person who had taught our data science courses left for industry, so I'd been assigned a graduate-level data science course that fall. Oh, and welcome back! Fortunately, mathematics is a strong preparation for many related fields, including data science. In this talk, I'll showcase how the simple concept of a function underpins huge areas of data work, from simple modeling to AI chatbots. In particular, the robust familiarity with functions that mathematics requires (e.g., complex domains and codomains, function spaces, etc.) lays the perfect foundation.