On Mon, 4 Aug 2003, Simon Fear wrote: > Peter is right, but there is a point here: it would be nice if > attach(my.dframe) would do nothing - or at least warn - if my.dframe was > already in the search list. Like library(). Attaching twice is almost
It is not like library(). attach attaches a copy of the data frame, and it can be altered subsequently. So how can you tell if the data frame is on the search list. I suspect it is quite common to create an object called `tmp' and put it on the search list for a while. library() assumes that you have not reinstalled a loaded package (and if you have you would get inconsistent results). > bound > to be an error? Not at all. > Of course in many circumstances it might be better to use with() than > attach() - if you haven't come across with(), it works like attach() > with an > inbuilt detach() when the parentheses close. > > Aside 1: it would also be nice if ?attach pointed to ?with. Is this kind > of > suggestion best sent to r-help or r-devel? I don't see they do the same job, especially not in an interactive session (which is when attach() is most usefully used in this way). > Aside 2: is with() efficient, or does it create a copy of the dataset? It does not create a copy, as you can see from the code (it uses a three-argument eval). -- 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 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
