Dimension of a vector
On Wed, 5 Dec 2007, maj at stats.waikato.ac.nz wrote:
Consider the following:
A <- 1:10 A
[1] 1 2 3 4 5 6 7 8 9 10
dim(A)
NULL
dim(A) <- c(2,5) A
[,1] [,2] [,3] [,4] [,5] [1,] 1 3 5 7 9 [2,] 2 4 6 8 10
dim(A)
[1] 2 5
dim(A) <- 10 A
[1] 1 2 3 4 5 6 7 8 9 10
dim(A)
[1] 10 Would it not make sense to have dim(A) = length(A) for all vectors?
No. A one-dimensional array and a vector are not the same thing. There are subtle differences, such as what names() means (see ?names). That a 1D array and a vector _print_ in the same way does occasionally lead to confusion, but then you also cannot tell from your printout that A has type "integer" and not "double".
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