[R] if (NULL) is error?

[Duncan Murdoch]

On 10/1/2006 12:29 PM, Alberto Vieira Ferreira Monteiro wrote:
> Why this is not valid?
> 
> test <- NULL
> if (test) "test"

The test part of an if statement should evaluate to a length 1 logical 
or numeric value.  NULL is length zero.

The R Language Definition explains this (although it implies length > 1 
is okay; in fact, that gives a warning).

Duncan Murdoch