Demonstration of how to split a data frame into a list when the grouping variable is a character string

dplyr_split.R

library(dplyr)

# use the iris dataset
dd <- iris

# The normal way to group or split is by directly referencing the var object
dd %>% group_by(Species)

dd %>% split(.$Species)

# If using this with a user defined reference to the variable such as 
# when doing this within a function, it is not obvious how to construct the 
# .$variable call properly as I would normally do this as a string.

# specify a character string reference to the variable to group by
g <- "Species"

# one can group with character strings
dd %>% group_by(.dots = g)

# Trying this with split fails
dd %>% split(.dots = g)

# or worse returns a list of length 1 that can then get passed on without
# one realising
dd %>% split(g)

# To emulate the splitting, we need the following which I found at
# https://stackoverflow.com/questions/39638233/grouped-data-frame-to-list
dd %>% split(., .[,g])

# Its not pretty, and doesnt match the dplyr syntax but it works.