[R] How to check the two different nulls?

[Erik Iverson]

blue sky wrote:
> x=list(a=1,b=NULL)
> is.null(x$b)
> is.null(x$c)
>
> Both the above two commands give me TRUE, but in the first one, b is
> NULL, in the second one, c doesn't exist. Are there functions that can
> help me distinguish the two different nulls?
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>   
?names