match.call with default arguments

Question

As part of a function, I want to output a list of all the arguments and their values, including the default values. For example, a function with these arguments:

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Answer 1

you can use a mix of the 2 , match.call and formals

foo <- function(x=NULL,y=NULL,z=2)
{
  ll <- as.list(match.call())[-1]     ## 
  myfor <- formals(foo)               ## formals with default arguments
  for ( v in names(myfor)){
             if (!(v %in% names(ll)))
                ll <- append(ll,myfor[v])  ## if arg is missing I add it
             }
  ll
}

For example :

  foo(y=2)
$y
[1] 2

$x
NULL

$z
[1] 2

> foo(y=2,x=1)
$x
[1] 1

$y
[1] 2

$z
[1] 2