Yes, indeed. The help page says that @ extracts the contents of a slot in S4 objects. But you mention below that this 'works' for S3 objects because S4 slots are stored as attributes. Doesn't this mean that @ is currently implemented to access attributes of objects in general (attributes of S3 objects or slots of S4 objects that are implemented as attributes)? I realize that this might change in the future...
-Christos > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Prof Brian Ripley > Sent: Thursday, March 27, 2008 3:17 AM > To: Christos Hatzis > Cc: r-help@r-project.org > Subject: Re: [R] Rule for accessing attributes? > > Oh please don't recommend misuse of @ to those already confused. > > @ is for accessing slots in S4 objects. This 'works' because > they happen to be stored as attributes. See the help page > (and the warning that it does no checking - we may change that). > > Similarly, > > plt$title <- "My Title" > > works because the package maintainer (of ggplot2, > unmentioned?) has chosen to set things up that way. R is > very flexible, and there is plenty of scope for package > authors to do confusing things. > > On Thu, 27 Mar 2008, Christos Hatzis wrote: > > > You need to use the '@' operator to directly access attributes (not > > elements) of objects: > > > >> [EMAIL PROTECTED] > > [1] "x" "y" "z" > > > > See ?'@' for more details. > > > > -Christos > > > >> -----Original Message----- > >> From: [EMAIL PROTECTED] > >> [mailto:[EMAIL PROTECTED] On Behalf Of Tribo Laboy > >> Sent: Thursday, March 27, 2008 12:16 AM > >> To: r-help@r-project.org > >> Subject: [R] Rule for accessing attributes? > >> > >> Hi ! > >> > >> I am a new user and quite confused by R-indexing. > >> > >> Make a list and get the attributes > >> lst <- list(x = 1:3, y = 4:6, z = 7:9) > >> attributes(lst) > >> > >> This returns: > >> > >> $names > >> [1] "x" "y" "z" > >> > >> I can easily do: > >> > >> nm <-names(lst) > >> > >> or > >> > >> nm <-attr(lst,"names") > >> > >> which both return the assigned names of the named list > 'lst', but why > >> then this doesn't work: > >> > >> lst$names > >> > >> ? > >> > >> I am confused ... Moreover, I noticed that some of the > objects (e.g. > >> plot objects returned by ggplot) also have attributes when > queried by > >> the 'attributes' function, but they are accessible by the > $ notation. > >> (e.g. > >> > >> xydf <- data.frame(x = 1:5, y = 11:15) plt <- ggplot(data = xydf, > >> aes(x = x,y = y)) + geom_point() > >> attributes(plt) > >> > >> Now we can change the title: > >> > >> plt$title <- "My Title" > >> plt > >> > >> So is it some inconsistency or am I missing something important? > >> > >> ______________________________________________ > >> 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. > > > > -- > 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 > > ______________________________________________ > 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.
