[R] use of "@" character in variable name

[Rolf Turner]

On 27/03/2009, at 2:52 PM, Marc Schwartz wrote:

>
> On Mar 26, 2009, at 8:40 PM, Rolf Turner wrote:
>
>>
>> On 27/03/2009, at 2:04 PM, Mike Miller wrote:
>>
>>> Importing data with a header row using read.delim, one variable
>>> should be
>>> named @5HTT but it is automatically renamed to X.5HTT, presumably
>>> because
>>> the "@" is either unacceptable or misunderstood.  I've tried to
>>> find out
>>> what the rules are on variable names but have been unsuccessful.
>>> I'll bet
>>> someone here can tell me where to look.  Maybe it's hidden away in
>>> here
>>> somewhere:
>>>
>>> http://cran.r-project.org/doc/manuals/R-data.pdf
>>
>> I don't know if there is a comprehensive list of the rules governing
>> variable names but the ``@'' sign is used to access ``slots'' under
>> S4 classes and methods.  See ?"@".  So it is (like?) an operation/
>> operator
>> and hence is ruled out just like ``+5HTT'' would be.  Reserved words
>> like
>> ``break'' and ``while'' are also excluded.  See fortune(18).
>>
>> Another rule is that a variable name can't begin with a digit.
>>
>> And it can't have white space in it.
>>
>> There are probably other rules, but essentially anything *sensible*
>> as a variable name can be used as a variable name.
>
>
> See ?make.names for more information, which is noted in the
> description of the 'check.names' argument in the read.table() family
> of functions.

It might also be useful to note that a list of reserved words can be  
found via

	?Reserved

(as I found out from ??"reserved words").

	cheers,

		Rolf Turner

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