On Wed, 13 Aug 2003, Richard A. O'Keefe wrote: > While reading through some of the R source code, I have come > across forms such as > m$... > m$... <- e > and I wondered what they meant. > > ?"$" mentions x$name, but not $...
... is a name, a special one in the context of function calls. > All it says is > > The operators `$' and `$<-' do not evaluate their second argument. > It is translated to a string and that string is used to locate > the correct component of the first argument. > > Does this mean that m$... is the same as m$"..." > and m$... <- e is the same as m$"..." <- e? Yes. > That's what it seems to do when I try it on some small data frames, > but is that ALL there is to it, or is there some special magic going > on? Is there any connection with the use of ... in formal and actual > parameter lists, or is it just accidental? Why would anyone _want_ > to use $... ? To add or to change (but almost always to remove) the component of a list named ... . And they occur frequently in matched calls. This construction (like many others) is explained in `S Programming': it seems you may find it enlightening. -- 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 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
