Extract list name passed to function as string in R [duplicate]-CodePudding

I am trying to extract the name of the list I am passing to a function as a string. The string extracted must be stored within the same function (so I can use it during the same call).

Example:

my_function <- function(obj, arg = NULL) {
  # obj is a list object that I pass to my_function()
  obj_string <- ... # obj_string is the name of the list I have just passed to my_function
}

so, if I write my_function(list_name), obj_string must store "list_name".

I tried with deparse(substitute(obj)) or deparse(substitute(Transform)) but they don't work. I have also tried {{obj}} but it won't work either.

CodePudding user response：

I finally managed to make it work myself (thanks to the other users who posted so far, I am going to test your answers too!)

as.character(as.list(match.call()[-1]$obj))

returns "list_name"

CodePudding user response：

We can use deparse/substitute. We don't need to create an object inside

 my_function <- function(obj, arg = NULL) { 
     deparse(substitute(obj))
}

-testing

> my_function(list_name)
[1] "list_name"

If we don't return anything. Just assign to an object and get the value or wrap with () to print into console

 my_function <- function(obj, arg = NULL) { 
    obj_string <- deparse(substitute(obj))
}

-testing

> tmp <- my_function(list_name)
> tmp
[1] "list_name"
> > (my_function(list_name))
[1] "list_name"

CodePudding user response：

You need to either return obj_string at the end of the function, or assign (<<-) it to the environment:

my_function <- function(obj, arg = NULL) {
  obj_string <- deparse(substitute(obj))
  obj_string
}

 #OR#

my_function <- function(obj, arg = NULL) {
  obj_string <<- deparse(substitute(obj))
}