Write a function that return string of passed objects

Question

I would like to create an R function called "test" with a single argument "object" which can be either a data frame or a list of data frames :

if object is a data frame, test() must return the name of the data frame as a string
if object is a list, test() must return a vector of strings where each element is the name of the data frames.

I would like test() to work with pipes %>% and |>.

What I tried :

test <- function(object) {
  return(deparse(substitute(object)))
}

# must return "iris"
iris |> test()
# must return "iris" "mtcars"
list(iris,mtcars) |> test()

Unfortunately with my test, it gives this :

> list(iris,mtcars) |> essai()
[1] "list(iris, mtcars)"

score 1 · Answer 1 · answered Feb 02 '23 at 13:31

1

test <- function(object) {
  if (class(object) == "list") {
    unlist(lapply(substitute(object), \(x) deparse(x)))[-1]
  } else {
    deparse(substitute(object))
  }
}

iris |> test()
# [1] "iris"

list(iris,mtcars) |> test()
# [1] "iris"   "mtcars"

answered Feb 02 '23 at 13:31

Merijn van Tilborg

5,452
1
7
22

Ok it works with |> but not with %>% : `list(iris, mtcars) %>% test()` # => returns character(0) – Damien Dotta Feb 02 '23 at 20:00
Your question was specific about `|>` but I cannot help you on `%>%` as I am not familiar enough using those and specifically how it acts on the data internally on the LHS. – Merijn van Tilborg Feb 03 '23 at 08:27
Perhaps this post may help you, https://stackoverflow.com/questions/30057278/get-lhs-object-name-when-piping-with-dplyr – Merijn van Tilborg Feb 03 '23 at 08:45

Talha Asif · Answer 2 · 2023-02-02T12:50:51.190

-1

Updated code:

test <- function(object) {
  if (class(object) == "data.frame") {
    return(deparse(substitute(object)))
  } else if (class(object) == "list") {
    return(unlist(lapply(object, function(x) deparse(substitute(x)))))
  } else {
    stop("Input must be a data frame or a list of data frames.")
  }
}

# must return "iris"
test(iris)
# must return c("iris", "mtcars")
test(list(iris, mtcars))

edited Feb 02 '23 at 12:50

answered Feb 02 '23 at 12:23

Talha Asif

349
1
9

Thanks but it doesn't work with list() as argument – Damien Dotta Feb 02 '23 at 12:34
and this has nothing to do with dplyr – Stéphane Laurent Feb 02 '23 at 12:43

Write a function that return string of passed objects

2 Answers2