dplyr's single-table verbs have scoped variants.
library(dplyr, warn.conflicts = FALSE)
d <- data.frame(
a = 1:4,
b = 1:4,
c = 1:4
)
d %>%
# a spoiler: funs() will be deprecated :P
mutate_at(vars(a, b), list(~ . * 2))
#> a b c
#> 1 2 2 1
#> 2 4 4 2
#> 3 6 6 3
#> 4 8 8 4
This is very handy. But, sometimes I feel the same thing can be achieved without the scoped ones if we have something like glue_quo() that takes raw expression and list of lists of symbols, and return the list of quosures. For example, I want
glue_quo(!!x := !!x * 2, list(x = syms(c("a", "b"))))
# or glue_quo(!!x := !!x * 2, list(x = c(a, b)))
would return list(a = quo(a * 2), b = quo(b * 2)) so that we can unquote it inside mutate() by !!!. But, I don't know how to implement it... This is what I tried and failed (Sorry for the terrible code 
):
col_syms <- syms(c("a", "b"))
col_envs <- lapply(col_syms, function(s) {
rlang::new_environment(list(x = s))
})
# do not unquote
expr_tmpl <- quote(rlang::quo(!!x := !!x * 2))
quos <- lapply(col_envs, rlang::eval_tidy, expr = expr_tmpl)
quos
#> [[1]]
#> <quosure>
#> expr: ^a := a * 2
#> env: 000000001E4FA038
#>
#> [[2]]
#> <quosure>
#> expr: ^b := b * 2
#> env: 000000001E50C620
d %>%
mutate(!!!quos)
#> Error in mutate_impl(.data, dots): Evaluation error: could not find function ":=".
Does anyone have a good idea?
Using expression is a chioce. Thanks!