On 8/14/06, Prof Brian Ripley <[EMAIL PROTECTED]> wrote: > On Mon, 14 Aug 2006, Henrik Bengtsson wrote: > > > In R-devel v2.4.0 NEWS: > > > > o The 'row.names' of a data frame may be stored internally as an > > integer or character vector. This can result in considerably > > more compact storage (and more logical row names from rbind) > > when the row.names are 1:nrow(x). However, such data frames > > are not compatible with earlier versions of R: this can be > > ensured by supplying a character vector as 'row.names'. > > > > This is great. > > > > With row.names == NULL for 1:nrow(x) the storage would be even more > > compact. > > A few bytes more compact. Some day you may get up to the next few lines > of NEWS which say > > The internal storage of row.names = 1:n just records 'n' for > efficiency with very long vectors. > > (BTW, this is four months' old news, hence my 'some day' comment.)
What is a very long vector? I would really like to see this for short vectors too, because in my case I would have half a million data frames with 10-20 rows (microarray data) and that adds up to 30-70Mb of memory. Just curious if you just store 'n', how do you tell if the row.names == n or 1:n? Thanks. /H > > > > I noticed that the number of rows is inferred from row > > names: > > > > > dim.data.frame > > function (x) > > c(length(attr(x, "row.names")), length(x)) > > <environment: namespace:base> > > > > but couldn't the number of rows be inferred from the first column, if > > there are no row names? I realize that this would break the case with > > zero-column data frames, e.g. > > > > > df <- data.frame(a=1:10) > > > df[,-1] > > NULL data frame with 10 rows. > > > > ...but maybe there is a way around that too. > > Yes, see above. > > -- > 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-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
