aes_loop cannot be used affectively outside of ggloop() (or at
least with access to the data frame names).
aes_loop(x, y, ...)
dplyr-like symbols (unqouted names) and
numerics/integers referencing the variable position within
data.aes_loop() returns an environment that includes aes.list (the
list of grouped aesthetic mappings used inside ggloop()) and a few
vectors used by other functions and lapply() loops for control (to
eliminate running duplicate code to return a result from a previously ran
function).
aes_loop2() returns a list of grouped mappings. This is similar to a
bunch of aes() mappings in a list waiting to be passed to
ggplot().
aes_loop() is solely meant to be called within
ggloop(). To create the raw list of grouped mappings, set
ggloop()'s gg_obs argument to FALSE.