Accessing variables in a function in R

Question

I was wondering if it is possible to simplify the code of the following function (i.e, if the part of the code: d0 = p$d0, d11 = p$d11, d12 = p$d12, k11 = p$k11, k12 = p$k12 can be replaced by some function) as I am just accessing the variables passed to the function trough the list p.

This is the R code of the function:

equation = function(p){

  d0 =  p$d0
  d11 = p$d11
  d12 = p$d12
  k11 = p$k11
  k12 = p$k12

  result = d0 + d11*k11 + d12*k12

  return(result)
}

equation(list(d0=1,d11=2,d12=3,k11=100,k12=1000))

Well you don't need to assign them to local variables. p$d0 + p$d11*p$k11 + p$d12*p$k12 could be the entire body of your function. — Dason
– Dason, Commented Dec 20, 2017 at 14:59
@Dason please suggest this as an answer before something more complicated (rather than simpler) gets accepted... — Spacedman
– Spacedman, Commented Dec 20, 2017 at 15:11
equation <- function(p) return(with(p, d0 + d11*k11 + d12*k12)) — jogo
– jogo, Commented Dec 20, 2017 at 15:27
@Spacedman I didn't write it as an answer because I didn't think the question was entirely appropriate. Seems more like a code review type thing. But I guess I'll put it as an answer since I do think it's probably the best approach for this particular problem and the other answers I'm not really a fan of. — Dason
– Dason, Commented Dec 20, 2017 at 16:08
You should post your solution as an answer rather than editing it into your question. — Gregor Thomas
– Gregor Thomas, Commented Feb 14, 2018 at 13:07

Dason · Accepted Answer · 2017-12-20 16:05:34Z

3

There is no need for anything fancy. You don't have enough that typing the p$ in front of each is overly burdensome and you don't need to assign anything locally. return isn't required so we can actually write your function with a single line body as:

equation <- function(p){
    p$d0 + p$d11*p$k11 + p$d12*p$k12
}

answered Dec 20, 2017 at 16:05

Dason

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Comments

Colin FAY · Accepted Answer · 2017-12-20 15:02:41Z

0

You can simply pass your elements as function arguments :

equation <- function(d0, d11, d12, k11, k12){
  d0 + d11*k11 + d12*k12
}

equation( d0=1, d11=2, d12=3, k11=100, k12=1000)
[1] 3201

Colin

answered Dec 20, 2017 at 15:02

Colin FAY

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Oriol Mirosa · Accepted Answer · 2017-12-20 15:07:47Z

0

Another option is to use the zeallot package, which has the unpacking assignment %<-%:

library(zeallot)

equation = function(p){
  c(d0, d11, d12, k11, k12) %<-% p

  result = d0 + d11*k11 + d12*k12

  return(result)
}

equation(list(d0=1,d11=2,d12=3,k11=100,k12=1000))
## 3201

answered Dec 20, 2017 at 15:07

Oriol Mirosa

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Vicente · Accepted Answer · 2018-02-15 13:48:07Z

0

I found the solution using list2env(p, envir = environment())

equation = function(p){

  list2env(p, envir = environment())

  result = d0 + d11*k11 + d12*k12

  return(result)
}

equation(list(d0=1,d11=2,d12=3,k11=100,k12=1000))

answered Feb 15, 2018 at 13:48

Vicente

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