Naming object in R from function input

Question

How do I create a variable from function input? For example,

test <- function(var_name, num) {
    var_name <<- 2 + num
}
test(hello, 2)

so hello will then be 4?

Not clear what you are asking. Waht is your expected result? — Pierre Lapointe
– Pierre Lapointe, Commented Jun 26, 2017 at 21:49
Functions in R are not meant to alter variables values outside their own scope. This is not a good design for R. Function should return values that you assign to variables; more like hello <- test(2) — MrFlick
– MrFlick, Commented Jun 26, 2017 at 21:56

Sraffa · Accepted Answer · 2017-06-26 22:02:49Z

2

I think what you want is something like this:

test <- function(var_name, num) {
    assign(var_name, num + 2, envir = .GlobalEnv)
}

test("hello", 2)

Here assign creates the varible var_name in the gobal environment (you need to set the envir parameter to .GlobalEnv to do that). Notice that the var_name parameter should be a string.

edited Jun 26, 2017 at 22:02

answered Jun 26, 2017 at 21:55

Sraffa

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1 Comment

Ben Bolker Over a year ago

or if you insist on test(hello,2) you can use assign(deparse(substitute(var)), num+2, envir=.GlobalEnv) -- but please see @MrFlick's comment above.

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