[Rd] Re: [R] suggestion for make.names
Prof Brian Ripley
ripley at stats.ox.ac.uk
Wed Jun 18 08:00:49 MEST 2003
Moved to R-devel, as it seems more appropriate to that audience and I
think has a slightly more liberal policy on attachments.
> I'm providing a new implementation (and documentation) of make.names
On Tue, 17 Jun 2003, Tom Minka wrote:
> I would like to suggest a modification to the make.names() function.
> The current implementation has two problems:
> 1. It doesn't check if a name matches an R keyword (like "function").
> 2. The uniqueness algorithm is not invariant to concatenation.
> In other words,
> make.names(c("a","a","a"),unique=T) !=
> The first problem means that you can construct a data frame for which
> there is no valid formula:
> lm(if~then, data.frame("if"=3,"then"=4))
> The second problem means that you get funny row names when you build
> up a data frame by concatenation:
> rbind(data.frame(x=1),data.frame(x=2),data.frame(x=3)) !=
> I'm providing a new implementation (and documentation) of make.names which
> fixes these problems. The uniqueness part is handled by make.unique, a
> useful function in its own right. For example, the following code in
> while(any(xj <- duplicated(rlabs)))
> rlabs[xj] <- paste(rlabs[xj], 1:sum(xj), sep = "")
> could be replaced by:
> rlabs = make.unique(rlabs)
> Another way to fix the first problem, by the way, would be to allow
> quoting in formulas, e.g. lm("if" ~ then, ...). Currently, when you
> do this it gives an error. This could eliminate the need for
> make.names in many cases, by being able to quote names like
> "New Jersey" or "log(x)".
Yes, we know and it is planned to allow that. However, R is a volunteer
project and that looks far from trivial and rather low priority. Now if
you have a patch for that we would be pleased to see it.
Brian D. Ripley, ripley at stats.ox.ac.uk
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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