如何在R中继续计算递归函数？

Question

I have a recursive function in R. I would like to track it and know how many times the function is called during the procedure. How can I do it in R?

EDIT: sample code:

test <- function(num)
{
  if(num>100)
    return(num)
  num <- num+4
  res <- test(num)
  return(res)
}

Answer 1

create a global variable using the <<- operator then index it in the recursive function.

counter <<- 0

then in your function that will be used recursively simply:

counter <<- counter +1

Answer 2

Another approach that does not require a global and <<- is:

test <- function(num, count=0) {
  if(num > 100)
    return(list(res=num, count=count))
  num <- num+4
  res <- test(num, count+1)
  return(res)
}

Note that the signature for invoking test is the same.

test(1)
##$res
##[1] 101
##
##$count
##[1] 25