Logo Questions Linux Laravel Mysql Ubuntu Git Menu
 

Count number of arguments passed to function

I'm interested in counting a number of arguments passed to a function. length can't be used for that purpose:

>> length(2,2,2,2,2)
Error in length(2, 2, 2, 2, 2) : 
  5 arguments passed to 'length' which requires 1

This is obvious as length takes 1 argument so:

length(c(2,2,2,2,2))

would produce the desired result - 5.

Solution

I want to call my function like that myFunction(arg1, arg2, arg3). This can be done with use of an ellipsis:

myCount <- function(...) {length(list(...))}

myCount would produce the desired result:

>> myCount(2,2,2,2,2)
[1] 5

Problem

This is awfully inefficient. I'm calling this function on substantial number of arguments and creating lists just to count number of objects is wasteful. What's the better way of returning the number of arguments passed to a function?

like image 428
Konrad Avatar asked Jan 05 '23 00:01

Konrad


1 Answers

How about

myCount <- function(...) {length(match.call())-1}

This just inspects the passed call (and removes 1 for the function name itself)

like image 169
MrFlick Avatar answered Jan 08 '23 07:01

MrFlick