"Simon Fear" <[EMAIL PROTECTED]> writes: > 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 > bound > to be an error?
The problem is, how can you tell? Consider f <- function() { d <- data.frame(x=1:10,y=rnorm(10)) attach(d) } f() f() This attaches two *different* dataframes, both called "d". > 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. I do occasionally speculate whether it would be possible to change attach() to be more like with(), but it's tricky business. > 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? R-devel, in principle, but developers will pick up hints from all over. R-bugs can also be used if you want to make sure that a suggestion is recorded (it may drown in the spam for a while, though...) R-bugs is best used for clear bugs, but a well-defined enhancement request can also get in there (do remember to label it as such, or it might generate a host of "Not a bug" responses.) > Aside 2: is with() efficient, or does it create a copy of the dataset? It converts the data frame to an environment, so I would suspect that it has to copy, but these things are "black magic": The paradigm in R is that of a functional language, where assignment merely attaches a label to computed objects. Objects are generally copied rather than modified in-place, but to avoid too much inefficiency there are a lot of special cases where we try to eliminate copying if possible. -- O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help