fluid.stats should take individual entries as well as lists

[rconstanzo]

I can see that for most use cases you'd be feeding fluid.stats a list as an input, but now with the @select interface, it's not inconceivable to have a single value needing rolling statistical summaries.

I tried for a bit just doing a float -> pack f f to "fake" having a list, but in the end just rolled my own next to it.

(also, having a derivative computed on the history would be nice too)

[tremblap]

you can also cheat by adding the word list in front of the float. we should consider creating an alias in the code @weefuzzy

[rconstanzo]

That works too, but just a bit of a funky/opaque interface thing.

I imagine the ship for this has sailed too, but having it output (optional?) derivatives too would be great, just to mirror the bufstats version. I basically rolled something like that for the SP-Tools thing and found it really useful on arbitrary metrics (delta times between attacks, arbitrary descriptors, etc...).