sym() creates a symbol from a string and
syms() creates a list of symbols from a
character vector.
enquo() and
enquos() delay the execution of one or
several function arguments. enquo() returns a single quoted
expression, which is like a blueprint for the delayed computation.
enquos() returns a list of such quoted expressions.
expr() quotes a new expression locally. It
is mostly useful to build new expressions around arguments
captured with enquo() or enquos():
expr(mean(!!enquo(arg), na.rm = TRUE)).
To learn more about tidy eval and how to use these tools, visit https://tidyeval.tidyverse.org and the Metaprogramming section of Advanced R.