Re: [R] function that uses a variable name as the parameter

From: Wacek Kusnierczyk <Waclaw.Marcin.Kusnierczyk_at_idi.ntnu.no>
Date: Wed, 12 Nov 2008 14:28:07 +0100

David Croll wrote:
> Hello dear R people!
>
>
> Several times it occurred to me that a function that uses a variable name as a parameter would be helpful, but I did not find out how to write such a function. I have experience in several programming language, but I did not come across a helpful trick...
>
> What I want to have is...
>
> a <- 12 # starting value
>
> add <- function(variable,increment) {
>
> variable <- variable + increment
>
> }
>
> # by typing a and 25 for example, you specify that 25 will be added to the variable a...
>
> add(a,25)
>
> # the new a equals 12 + 25 = 37
>
>

add = function(variable, value)

   assign(deparse(substitute(variable)), variable + value, envir=parent.frame())

a = 1
add(a, 2)
a
# 3

addtoa = function(value)

   add(a, value)
addtoa(10)
a
# still 3

add = function(variable, value)

   assign(deparse(substitute(variable)), variable + value, inherits=TRUE)

addtoa(10)
a
# 13

?assign

vQ



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