On Sat, Jul 7, 2018 at 3:48 PM, Ott Toomet <otoo...@gmail.com> wrote: > Thanks, Hadley for bringing this up:-) > > I am teaching R and I can suggest 5 different definitions of 'vector': > > a) vector as a collection of homogeneous objects, indexed by [ ] (more > precisely atomic vector). Sometimes you hear that in R, "everything is a > vector", but this is only true for atomic objects. > b) vector as a collection of objects, indexed by either [ ] and [[ ]]. This > includes atomic vectors and lists. > c) vector versus scalar. It pops up when teaching math and stats, and is > somewhat confusing, in particular if my previous claim was that "R does not > have scalars". > d) vector versus matrix (or other arrays). Again, it only matters when > doing matrix operations where 'vectors', i.e. objects with NULL dimension, > behave their own way. > e) finally, 'is.vector' has it's own understanding what constitutes a > vector.
Yes! And to add to the confusion there are three meanings to numeric vector: * As an alias for double (i.e. numeric() and as.numeric()) * To refer to integer and double types jointly (as is S3 and S4 class) * A vector that behaves as if it is a number (e.g. is.numeric(), which excludes factors) Hadley -- http://hadley.nz ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel