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?
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
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 
variableto be a free variable, you can create a closure around it, but it won't change the function definition. Is this just a display issue? Or is there some behavior that you are trying to change?force(variable).