On Tue, 12 Aug 2003, Spencer Graves wrote: > "a$b" = "a[['b']] = attribute "b" of list "a".
(Not quite always. First, it is `component' not `attribute' and second $ and [[ ]] do behave differently, e.g. for data frames in 1.7.x.) > A basic object in R is a list, and the "$" operator provides one means > of accessing named attributes of a list. > > Beginning with R 1.7, objects can also have "slots", which are > accessed as "[EMAIL PROTECTED]". I have yet to understand why "slots" were > introduced; perhaps someone else will explain this. Slots are part of objects which have formal (S4) classes, made using the `methods' package (so have been around since at least R 1.4.0). They are an implementation of the ideas of Chambers (1998). Formally classed objects are not just lists: they have rules for the number, names and types of the slots. (Currently they are lists, but that's an implementation detail.) -- 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
