It's going to be harder to do just about anything related to data analysis in Haskell than in R. In R I can load a dataset, do some formatting, and produce a well designed plot in fewer than 5 lines of code. Haskell might run faster, and it's certainly more versatile, but for data analysis it isn't even comparable.

Could you expand on why? I'll be starting a data-heavy side project and have meant to make an effort with Haskell for a while

I always thought that R is fairly unmatched in both breadth and depth for statistical work and general data analysis, with the Python stack in second (e.g., numpy+scipy+pandas+...).

People use R as a convenient tool.i.e., R users are tool/library users, not tool builders in general. Haskell cannot compete with R for this user base.