Hierarchical or multi-index for data frames

Again, thank you so much for your input.

Then there are currently two generic interfaces: Tables (which replaces DataStreams) and TableTraits. There’s hope that we could agree on a single common interface, but it’s still under discussion.

This thread really puts Tables.jl into context.

@piever: I really liked the two tutorials you linked. And nesting arrays into DataFrame seems really creative. Definitely has potential although probably not as standard operating procedure, like you said.