Re: [Rd] Is NULL a vector?
On Mon, Jul 23, 2018 at 2:17 PM, Duncan Murdoch wrote: > On 23/07/2018 3:03 PM, Hadley Wickham wrote: >> >> Hi all, >> >> Would you generally consider NULL to be a vector? > > > According to the language definition (in the doc directory), it is not: > "Vectors can be thought of as contiguous cells containing data. Cells are > accessed through indexing operations such as x[5]. More details are given in > Indexing. > > R has six basic (‘atomic’) vector types: logical, integer, real, complex, > string (or character) and raw. The modes and storage modes for the different > vector types are listed in the following table." > > and later > > "There is a special object called NULL. It is used whenever there is a need > to indicate or specify that an object is absent. It should not be confused > with a vector or list of zero length." Perfect, thanks! Also available online at https://cran.r-project.org/doc/manuals/r-release/R-lang.html#Vector-objects Hadley -- http://hadley.nz __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] Is NULL a vector?
On 23/07/2018 3:03 PM, Hadley Wickham wrote: Hi all, Would you generally consider NULL to be a vector? According to the language definition (in the doc directory), it is not: "Vectors can be thought of as contiguous cells containing data. Cells are accessed through indexing operations such as x[5]. More details are given in Indexing. R has six basic (‘atomic’) vector types: logical, integer, real, complex, string (or character) and raw. The modes and storage modes for the different vector types are listed in the following table." and later "There is a special object called NULL. It is used whenever there is a need to indicate or specify that an object is absent. It should not be confused with a vector or list of zero length." Duncan Murdoch Base R functions are a little inconsistent: ## In favour ``` r identical(as.vector(NULL), NULL) #> [1] TRUE identical(as(NULL, "vector"), NULL) #> [1] TRUE # supports key vector vector generics length(NULL) #> [1] 0 NULL[c(3, 4, 5)] #> NULL NULL[[1]] #> NULL ``` ## Against ``` r is.vector(NULL) #> [1] FALSE is(NULL, "vector") #> [1] FALSE ``` ## Abstentions ``` r is.atomic(NULL) #> [1] TRUE # documentation states "returns NULL if x is of an atomic type (or NULL)" # is "or" exclusive or inclusive? ``` Hadley __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
[Rd] Is NULL a vector?
Hi all, Would you generally consider NULL to be a vector? Base R functions are a little inconsistent: ## In favour ``` r identical(as.vector(NULL), NULL) #> [1] TRUE identical(as(NULL, "vector"), NULL) #> [1] TRUE # supports key vector vector generics length(NULL) #> [1] 0 NULL[c(3, 4, 5)] #> NULL NULL[[1]] #> NULL ``` ## Against ``` r is.vector(NULL) #> [1] FALSE is(NULL, "vector") #> [1] FALSE ``` ## Abstentions ``` r is.atomic(NULL) #> [1] TRUE # documentation states "returns NULL if x is of an atomic type (or NULL)" # is "or" exclusive or inclusive? ``` Hadley -- http://hadley.nz __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
