[R] deciphering help for `attach`

[PIKAL Petr]

Hi.

I strongly recommend not to use attach. I agree that mentioned statements are rather contradictory and probably others could give you more insightful answer. You could consider that by attaching some data, you create something like a copy of original data in your system with a feature that you can use column names directly. If you change something in the data after attachment, you change only attached version and not an original.

It is similar as if you take a picture of Gioconda an use some creativity to add a moustache to this picture. In any circumstances moustache does not propagate to the original Louvre painting. Do not perform any tricks, preferably do not perform attach.

Cheers
Petr

> -----Original Message-----
> From: R-help <r-help-bounces using r-project.org> On Behalf Of Edward McNeil
> Sent: Monday, April 27, 2020 2:07 PM
> To: r-help using r-project.org
> Subject: [R] deciphering help for `attach`
> 
> Hi,
> I have two related questions.
> 
> 1. In the help page for `attach` under "Details" it says in paragraph 3:
> "By default the database is attached ..."
> 
> But then paragraph 4 starts: "The database is not actually attached."
> 
> Could somebody explain this contradiction? Is the data(base) attached or
> not?
> 
> 2. What is meant by the 5th paragraph: "One useful ‘trick’ is to use what =
> NULL (or equivalently a length-zero list) to create a new environment on the
> search path into which objects can be assigned by `assign` ... "?
> 
> I don't understand what this "trick" is or why a "trick" needs to be performed
> here.
> 
> Thanks
> --
> Edward McNeil
> 
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.