The ... argument is a special argument that can be used to pass a variable number of arguments to a function. However, any arguments that appear after ... on the argument list must be named explicitly and cannot be partially matched or matched positionally.
This is because the ... argument is used to pass a variable number of arguments to the function. If any arguments were allowed to be matched positionally after the ... argument, it would be difficult to determine which arguments were passed to the function and which arguments were part of the ... argument.
For example, the following code would not work as expected:
paste("a", "b", sep = ":", se = " ")
In this code, the argument se is matched positionally after the ... argument. However, the ... argument can contain any number of arguments, so it is not possible to determine whether se is part of the ... argument or a positional argument.
To fix this code, the argument se must be named explicitly:
paste("a", "b", sep = ":", se = " ")
This code would now work as expected, and the string "a:b " would be printed to the console.
It is important to remember that any arguments that appear after the ... argument must be named explicitly. This is to ensure that the function knows which arguments are passed to the function and which arguments are part of the ... argument.
