That's as documented, on the help page. (NULL is a zero-length argument.) There's even a reason given.
Exactly which part of the help page did you not understand? On Tue, 29 Jul 2003 [EMAIL PROTECTED] wrote: > R-Version: 1.7.1 (2003-06-16) > OS: Debian/GNU Linux > > cbind and rbind handle NULL parameters inconsistently. > > Consider: > > cbind() > NULL > > cbind(NULL) > NULL > > And: > > cbind(diag(x = 1, 1, 1)) > [,1] > [1,] 1 > > cbind(NULL, diag(x = 1, 1, 1)) > [,1] > [1,] 1 > > These seem to indicate that NULL parameters will be ignored in any call to > cbind and rbind. However: > > > cbind(NULL, diag(x = 1, 0, 1)) > [,1] [,2] > > I.e. if one dimension of another parameter to cbind/rbind is zero, > cbind/rbind will create a row/column from the NULL parameter. > > This inconsistency creates problems in the construction of matrices within > loops and similar constructs. So? It's a documented feature. -- 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-devel
