[Rd] assigning NULLs to elements of a list

Stephen B. Weston weston at lindaspaces.com
Tue Feb 12 16:00:54 CET 2008

Oleg Sklyar wrote:
> Dear developers:
> I have just came across an (unexpected to me) behaviour of lists when 
> assigning NULLs to list elements. I understand that a NULL is a valid R 
> object, thus assigning a NULL to a list element should yield exactly the 
> same result as assigning any other object. So I was surprised when 
> assigning a NULL in fact removed the element from the list. Is this an 
> intended behaviour? If so, does anybody know where is it documented and 
> what is a good way around?

This topic is discussed in the R FAQ, in section 7.1 "How can I set 
components of a list to NULL?"  It also shows up in section 3.3.3,
in the context of incompatibilities with S.

- Steve

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