Another research project from this year that tackles multi-touch visualizations: Ramik Sadana's and John Stasko's Designing and implementing an interactive scatterplot visualization for a tablet computer. The authors came up with several neat interaction techniques for massaging the data presented in a scatterplot in various ways.
When I saw the excellent presentation by Ramik at AVI 2014 back in May, I was very reminded of my own Touchwave project - different visualization technique (scatterplots instead of stacked graphs), but related interactions based on the vocabulary of the iPad. I guess just one more such touchification paper until we see a taxonomy for touch-based interactions published...
Anyway, here's the video: