CODEWITHSUNDEEP
r
Dan
Dan

Reputation: 12074

R: adding an argument to match.call output

Say I have the following function in R:

tst <- function(x,y){
  foo <- match.call()
  print(foo)
}

tst(4,5)

This gives tst(x = 4, y = 5). Awesome. Now, I want to add an argument.

tst <- function(x,y){
  foo <- match.call()
  foo[[length(foo)+1]] <- 6
  print(foo)
}

tst(4,5)

This prints tst(x = 4, y = 5, 6), which is great. However, I need to add an argument name so that the function knows what to do with it. For example, I want it to be tst(x = 4, y = 5, z = 6). I tried simply foo[[length(foo)+1]] <- "z = 6", but that clearly doesn't work. I've also toyed with parse and eval without success. Any suggestions?

Upvotes: 2

Views: 292

Answers (1)

Spacedman
Spacedman

Reputation: 94182

You can actually treat the call like a list and give it a named argument:

> tst =
function(x,y){
 foo = match.call()
 foo[["this"]] ="that"
 print(foo)
}
> tst(x=2,y=3)
tst(x = 2, y = 3, this = "that")

Upvotes: 3

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