converting character vector to unquoted names of objects

Question

How can I pass a character vector naming existing objects to a function that only accepts unquoted names of existing objects?

devtools::use_data(..., )
?use_data: ...   Unquoted names of existing objects to save.

for example an alternative interface is provided by ?save():

base::save(..., list=, ) 
?save: list   A character vector containing the names of objects to be saved.

Example:

x <- "hello"
y <- "world"
save(x, y, file="./test.rda") # works fine
save(c("x", "y"), file="./test.rda")
>> Error in save(c("x", "y"), file = "./test.rda") : Objekt ‘c("x", "y")’ nicht gefunden

I'm sure this has been asked and answered many times but I couldn't find a solution. I unsuccesfully tried with the usual suspects as.name(), noquote(), get(), eval(), parse(), substitute(), etc.

The closest I got was

unquote(c("x", "y")

Thanks for any help or redirection

In this specific case you can do : save(list = c("x", "y"), file="./test.rda") — moodymudskipper
– moodymudskipper, Commented Aug 13, 2018 at 9:59
The example you chose might not be the best because save accepts character arguments as well as names. so this would work as well : do.call(function(...) save(...,file="./test.rda"), as.list(c("x", "y"))) though you might want something looking more like do.call(function(...) save(...,file="./test.rda"), lapply(c("x", "y"), as.name)) for other cases. — moodymudskipper
– moodymudskipper, Commented Aug 13, 2018 at 10:05
@Moody_Mudskipper Can you sove the problem by not using list= but the ... argument for input, in save(), like I am forced to do in use_data(...,)? — rluech
– rluech, Commented Aug 13, 2018 at 12:47
That's what I'm doing with the 2nd option of my second comment — moodymudskipper
– moodymudskipper, Commented Aug 13, 2018 at 12:48
Your answer will be enough ;), and better to use the form you used. If you use rlang/tidyverse you can also use invoke(save, lapply(obj, as.name), file="./test.rda") which is less awkward to deal with additional arguments. — moodymudskipper
– moodymudskipper, Commented Aug 13, 2018 at 14:15

rluech · Accepted Answer · 2018-08-13 14:04:23Z

4

And this would be the answer based on @Moody_Mudskipper's comment

x <- "hello"
y <- "world"
obj <- c("x", "y")
do.call(save, c(lapply(obj, as.name), file="./test.rda"))

analog with devtools::use_data()

answered Aug 13, 2018 at 14:04

rluech

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