Hi all,
Is there are base function that I've missed that tests if an object is
a vector in the dimensionality sense, rather than the data structure
sense? i.e. something that checks is.null(dim(x)) ?
is.vector() is trivially disqualified since it also checks for the
presence of non-names attributes:
x <- factor(c("a", "a", "b"))
is.vector(x)
#> [1] FALSE
is.null(dim(x))
#> [1] TRUE
Hadley
--
http://hadley.nz
On 07/07/2018 1:20 PM, Hadley Wickham wrote:> Hi all, > > Is there are base function that I've missed that tests if an object is > a vector in the dimensionality sense, rather than the data structure > sense? i.e. something that checks is.null(dim(x)) ? > > is.vector() is trivially disqualified since it also checks for the > presence of non-names attributes: > > x <- factor(c("a", "a", "b")) > is.vector(x) > #> [1] FALSE > > is.null(dim(x)) > #> [1] TRUE >I don't know of one. I can't think of nontrivial cases where that distinction matters; do you know of any where base functions act differently on vectors and 1D arrays? (A trivial example is that dimnames(x) gives different results for a named vector and an array with dimnames.) Duncan Murdoch
On Sat, Jul 7, 2018 at 12:54 PM, Duncan Murdoch <murdoch.duncan at gmail.com> wrote:> On 07/07/2018 1:20 PM, Hadley Wickham wrote: >> >> Hi all, >> >> Is there are base function that I've missed that tests if an object is >> a vector in the dimensionality sense, rather than the data structure >> sense? i.e. something that checks is.null(dim(x)) ? >> >> is.vector() is trivially disqualified since it also checks for the >> presence of non-names attributes: >> >> x <- factor(c("a", "a", "b")) >> is.vector(x) >> #> [1] FALSE >> >> is.null(dim(x)) >> #> [1] TRUE >> > > I don't know of one. I can't think of nontrivial cases where that > distinction matters; do you know of any where base functions act differently > on vectors and 1D arrays? (A trivial example is that dimnames(x) gives > different results for a named vector and an array with dimnames.)I was thinking primarily of completing the set of is.matrix() and is.array(), or generally, how do you say: is `x` a 1d dimensional thing? (I don't have any feel for whether the check should be is.null(dim(x)) vs. length(dim(x)) <= 1) Hadley -- http://hadley.nz