CODEWITHSUNDEEP
rfunctionvariablesfunction-definitionfunction-declaration
Imsa
Imsa

Reputation: 89

Avoid names of variables ending into function definitions in R

I would like to use values within variables for defining functions in R. However, after declaring the function I can still see the variable names instead of their values inside the function definition. Here is an example:

> variable <- 10
> fn <- function() {message(variable*2)}
> fn
function() {message(variable*2)}

And what I am expecting to see:

> variable <- 10
> fn <- function() {message(variable*2)}
> fn
function() {message(10*2)}

How could I fix this?

Upvotes: 0

Views: 88

Answers (2)

G. Grothendieck
G. Grothendieck

Reputation: 270045

Rather than modify the function code wrap the variable together with the function in the same environment using local . (Depending on what is in the function you may need to add the envir = .GlobalEnv argument to local.)

fn <- local({
  variable <- 10
  function() {message(variable*2)}
})

fn()
## 20

Upvotes: 3

user2554330
user2554330

Reputation: 44957

Like @MrFlick in his comment, I don't know why you would want to do this. But in case you have a reason for it, here's one way to do it:

fn <- function() 1 # dummy declaration

body(fn) <- substitute(
  # The body of the function
  {message(variable*2)},  
     
  # The substitutions you want                  
  list(variable = 10)) 

fn
#> function () 
#> {
#>     message(10 * 2)
#> }

Created on 2024-09-05 with reprex v2.1.1

Edited to add:

I just read your response to his comment. I think you are taking the wrong approach here. This is a better way to do what you want:

makeFn <- function(variable) {
  force(variable)   # Make sure it is evaluated
  function() {message(variable*2)}
}

fn10 <- makeFn(10)
fn20 <- makeFn(20)
fn10()
#> 20
fn20()
#> 40

Created on 2024-09-05 with reprex v2.1.1

Upvotes: 3

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