[R] $ operator is invalid for atomic vectors, returning NULL - what is the right thing to do then?

Duncan Murdoch murdoch at stats.uwo.ca
Thu Dec 6 15:51:38 CET 2007

On 12/6/2007 7:04 AM, Søren Højsgaard wrote:
> Dear all,
> Starting from a recent version of R, the $ became "unusable" on atomic vectors, e.g.
>> x <- c(a=1,b=2)
>> x$a
> Warning message:
> In x$a : $ operator is invalid for atomic vectors, returning NULL
> I can of course do
>> x['a']
> - but that requires more typing (5 characters rather than 2). 
> Apologies if I've missed a an announcement regarding this, but
> 1) Is there an alternative to the ['a'] and
> 2) Why was this change made?

There's an announcement in the NEWS file for 2.6.0


     o	$ on an atomic vector now gives a warning that it is 'invalid'.
	It remains deprecated, but may be removed in R >= 2.7.0.

and an update in R-devel saying that in fact it has been made defunct there.

In answer to your questions:

1) I don't think so, other than x[1].
2) I don't remember the details, other than it was to avoid confusion. 
Maybe someone else can summarize the discussion?

Duncan Murdoch

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