After the discussion a while back about how sort inconsistently handles attributes such as dim's, I have taken a closer look and found yet more anomalies. That suggested trying out the principle that sort() should preserve only names (and sort those). Now, sort(partial=) was preserving names and NOT sorting them, and since it was included for efficiency I decided it should just drop names. One consequence of this is that sort() would drop S3 classes (which is necessary for e.g. time-series-like classes). I have tested this out over CRAN packages and it is currently live in R-devel. The only thing I can see it breaks is lattice (sorry Deepayan, please take a look at the changes made to axis.Date whose code you borrowed). Given that this is close to what S does and sort() was not documented to preserve attributes, I was not expecting much impact from this change. Since it seems to have minimal impact this seems the best way forward, but I am open to counter-proposals.
Brian D. Ripley, ripley at stats.ox.ac.uk 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