On Thu, 6 Dec 2007, Søren Højsgaard wrote:
Dear all,
Starting from a recent version of R,
From R 2.5.0, not so recent.
the $ became "unusable" on atomic vectors, e.g.
x <- c(a=1,b=2)
x$a
NULL
Warning message:
In x$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?
It has always returned NULL on atomic vectors: see the help page.
E.g. in R 2.0.0 from 2004:
x <- c(a=1,b=2)
x$a
NULL
x['a']
a
1
The warning was added three versions of R ago: the announcement is in the
NEWS file for 2.5.0.
USER-VISIBLE CHANGES
o Using $ on an atomic vector now raises a warning, as does use
on an S4 class for which a method has not been defined.
I think you have exemplified the answer to your question '2)': because
users misunderstood what it did.
In R 2.7.0 this will be an error, since package programmers did not seem
to be heeding the warnings.
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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