How to convert variable (object) name into String [duplicate]

Question

I have the following data frame with variable name "foo";

 > foo <-c(3,4);

What I want to do is to convert "foo" into a string. So that in a function I don't have to recreate another extra variables:

   output <- myfunc(foo)
   myfunc <- function(v1) {
     # do something with v1
     # so that it prints "FOO" when 
     # this function is called 
     #
     # instead of the values (3,4)
     return ()
   }

Just curious - why do you need to get object name from an object? — CHP
– CHP, Commented Jan 29, 2013 at 7:21
I have a sample use: I have a function that takes as argument a vector, and append the values of that vector into a column in a dataframe. I also need to populate into another column the source of the value, which is the name of the initial vector. Voila. — Ricky
– Ricky, Commented Jan 27, 2015 at 3:46
@ChinmayPatil It may be useful to pass the string name of the object to its output file name, for instance. — fred
– fred, Commented Apr 11, 2019 at 21:09
My two cents: a plotting function using the given variable names as labels / legend — annhak
– annhak, Commented Sep 6, 2021 at 7:37

Sven Hohenstein · Accepted Answer · 2014-01-25 07:30:43Z

319

You can use deparse and substitute to get the name of a function argument:

myfunc <- function(v1) {
  deparse(substitute(v1))
}

myfunc(foo)
[1] "foo"

edited Jan 25, 2014 at 7:30

answered Jan 29, 2013 at 7:37

Sven Hohenstein

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8 Comments

Sven Hohenstein Over a year ago

@MahdiJadaliha You can try this function: myfunc <- function(v1) { s <- substitute(v1); if (length(s) == 1) deparse(s) else sub("\\(.", "", s[2]) }.

theforestecologist Over a year ago

How would you do this with multiple objects? Specifically, how would you do it in a way to get separate strings for each object name? (For example, if I had object foo, foo1, and foo2 and I wanted to create a list of their names as separate character strings).

Sven Hohenstein Over a year ago

@theforestecologist If the function has multiple parameters, you can use deparse(substitute(.)) for each parameter, store the result in a variable, and put the variables in a list afterwards.

SumNeuron Over a year ago

@SvenHohenstein this doesn't work when you use a for loop...

cloudscomputes Over a year ago

you can also use deparse(quote(var)) in which quote freeze the var from evaluation and deparse which is the inverse of parse make the symbol back to string

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