Even though Wolfram has not (yet? hope always dies last!) released a version of Mathematica for the iPad (meaning, a frontend notebook coupled to an actual onboard computing kernel) they have released a client for “Wolfram Online” (often referred to as “Cloud Mathematica”) offering. This isn’t quite what I would like, as there’s a significant range of circumstances where I cannot rely on network access (such as when flying) but for most other situations it suits the purpose.
Other mathematics-inclined apps allow even greater range of onboard functionality (Pythonista, MathSudio spring to mind).
Upshot: one can most definitely do significant amounts of data analysis on an iPad.
Which is way I had to switch back from OpenBSD (which doesn’t run it) and Linux (which until today’s update, didn’t have HiDPI support) back to Mac OS.
I wouldn't use an iPad for this though. The shell's are all a compromise and I'm waiting for a great e-ink display so I can remote from a park / beach / patio.