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.
