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

[Rolf Turner]

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.

	cheers,

		Rolf Turner

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