Re: [Rd] attach and object masking

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Fri 10 Jun 2005 - 16:32:43 GMT

On Fri, 10 Jun 2005, Martyn Plummer wrote:

> The library() function prints an information message when objects are
> masked on the search path by (or from) a newly attached package. The
> attach() function, however, doesn't. Is there a good reason for this?
> I have adapted the machinery for checking conflicts used in the library
> () function to attach(). If there are no objections, I will check this
> into R-devel.
>
> I have seen new users get into terrible trouble with attach, e.g.
> 1) attaching the same database multiple times, or
> 2) Masking a vector in an attached data frame with a transformed version
> in the global environment and *then* re-running a script that transforms
> the transformed variable. For example, run this snippet twice and you
> might get a surprise.
>
> foo <- data.frame(x=1:10)
> attach(foo)
> x <- x/2
>
> A warning would certainly help.
>
> Incidentally, (1) occurs in the example for the beavers data set. I
> didn't find any other problems.

Not so: it attaches different dfs with the same column names. I think that is quite common and normally intentional. (Not cleaning up is not good practice though, and that example can be improved a lot.)



R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel Received on Sat Jun 11 02:35:52 2005

This archive was generated by hypermail 2.1.8 : Mon 24 Oct 2005 - 22:27:16 GMT