Hi in interactive sessions it is convenient way to call data frame columns and repeatedly use them in calculations. You just have to be careful with some functions as they can be useful but dangerous.
rm(something) removes an object from environment without warning. It is usually not a fault of a program, when something gets wrong. Regards Petr > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Pierrick Bruneau > Sent: Thursday, March 21, 2013 9:13 AM > To: Michael Weylandt > Cc: r-help@r-project.org > Subject: Re: [R] problem subsetting data.frame in R version 2.15.2 for > Windows > > OK, I just had a look at the Good Practice section of ?attach, it > indeed looks bad... > > Maybe this danger should be emphasized in ?attach, or the function even > deprecated (why maintaining ugly patterns when better solutions exist?) > > > On Thu, Mar 21, 2013 at 8:58 AM, Michael Weylandt < > michael.weyla...@gmail.com> wrote: > > > > > > > On Mar 21, 2013, at 7:39, Pierrick Bruneau <pbrun...@gmail.com> > wrote: > > > > > Hi Borja, > > > > > > You may issue: > > > > > > attach(data) > > > > No -- bad idea -- dangerous -- confusing statefulness, etc. (See > > explanations in the archives as to why) > > > > > > > > which results in adding your column names to the search path of R > > > for > > name > > > resolving. > > > > > > Pierrick Bruneau > > > CRP Gabriel Lippmann > > > > > > > > > On Wed, Mar 20, 2013 at 11:17 PM, Borja . > <borjalato...@outlook.com> > > wrote: > > > > > >> Good day. > > >> I create a data frame like this: > > >>> data <- data.frame(a=1:10,b=11:20,c=21:30) > > >> I can subset this data.frame by saying: > > >>> data[data$a>7,] > > >> and I get this result > > >> a b c 8 8 18 28 > > >> 9 9 19 29 10 10 20 30 > > >> I understand I should get the same result by saying > > >>> data[a>7,0] > > >> but I don't. Instead I get: > > >> Error in `[.data.frame`(data, a > 7, 0) : object > 'a' > > >> not > > > > Try instead > > > > with(dat, dat[a > 0, ]) > > > > for a cleaner option. > > > > MW > > > > > > >> found > > >> Thank you very much in advance > > >> [[alternative HTML version deleted]] > > >> > > >> ______________________________________________ > > >> R-help@r-project.org mailing list > > >> 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. > > > > > > [[alternative HTML version deleted]] > > > > > > ______________________________________________ > > > R-help@r-project.org mailing list > > > 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. > > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > 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. ______________________________________________ R-help@r-project.org mailing list 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.
