Olivia Lau <olau <at> fas.harvard.edu> writes: : : Hi all, : : I'm not sure if this is a feature or a bug (and I did read the : FAQ and the posting guide, but am still not sure). Some of my : students have been complaining and I thought I just might ask: : Let K be a vector of length k. If one types dim(K), you get : NULL rather than [1] k. Is this logical? : : Here's the way I explain it (and maybe someone can provide a : more accurate explanation of what's going on): R has several : types of scalar (atomic) values, the most common of which are : numeric, integer, logical, and character values. Arrays are : data structures which hold only one type of atomic value. : Arrays can be one-dimensional (vectors), two-dimensional : (matrices), or n-dimensional. : : (We generally use arrays of n-1 dimensions to populate : n-dimensional arrays -- thus, we generally use vectors to : populate matrices, and matrices to populate 3-dimensional : arrays, but could use any array of dimension < n-1 to populate : an n-dimensional array.) : : It logically follows that when one does dim() on a vector, one : should *not* get NULL, but should get the length of the vector : (which one *could* obtain by doing length(), but I think this is : less logical). I think that R should save length() for lists : that have objects of different dimension and type. :
In R, vectors are not arrays: R> v <- 1:4 R> dim(v) NULL R> is.array(v) [1] FALSE R> a <- array(1:4) R> dim(a) [1] 4 R> is.array(a) [1] TRUE ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
