在已处理的参数上定义默认的R函数参数

Question

I'm writing a package function that needs defaults parameters to work, but whose values have to be taken from processed (other) arguments of the function. As of now, I'm doing it like so :

myfunc <- function(x, y, n=NULL){
  processed <- some_other_func(x,y)
  x <- processed$x
  y <- processed$y
  if(is.null(n)){
    n <- length(intersect(x,y))/3
  }
  # do stuff
}

But ideally, I'd like a default expression to be put instead of NULL because it seems inconsistent if my doc says that the default is length(intersect(x,y))/3 .

Do you know of a way I could specify the default parameter to be more comprehensible ?

Answer 1

Maybe you could solve it something like this?

default_function <- function(v1, v2)
{
  return((v1 + v2)/2)
}

dummy_function <- function(x, y, n = default_function)
{
  x = x
  y = y
  if(class(n) == "function") n = n(x,y) # if n is any kind of function do it

  print(paste(x, y, n))

}


dummy_function(1, 2)
dummy_function(1, 2, 100)