On Sat, 15 Mar 2008, Gabor Csardi wrote: > On Sat, Mar 15, 2008 at 04:33:32PM +0100, Christophe Genolini wrote: >> Hi the list >> >> Is it possible to create an empty matrix ? I do not mean an matrix with >> a single value that is NA (which is not empty) but a real empty one, >> with length=0. > > Sure: > >> matrix(nrow=0, ncol=5) > [,1] [,2] [,3] [,4] [,5] >> a <- array( dim=c(5,4,0) ) >> dim(a) > [1] 5 4 0 >> length(a) > [1] 0 > >> I do not understand why we have length(numeric()), length(factor()) and >> length(character()) to zero, and length(array()) to one... Any rason for >> that ? > > That i don't know, maybe someone else does.
See the reference on the help page for array and section 3.3.3 of the R FAQ (about the 16th item). When R was first developed, S did not allow zero dimensions and so the minimum length for an array (or matrix) was one. -- 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.
