[Rd] A weird behaviour of strsplit?

[Duncan Murdoch]

On 18/12/2019 9:42 a.m., IAGO GINÉ VÁZQUEZ wrote:
> Hi all,
> 
> In the help of strsplit one can read
> 
> split   character vector (or object which can be coerced to such) containing regular expression<http://127.0.0.1:39783/help/library/base/help/regular%20expression>(s) (unless fixed = TRUE) to use for splitting. If empty matches occur, in particular if split has length 0, x is split into single characters. Ifsplit has length greater than 1, it is re-cycled along x.
> 
> Taking into account that split is said to be a vector (not a length 1 vector) and the last claim above, I would expect that the output of
> 
> 
> strsplit("3:4", split = c(",",":"), fixed = TRUE)
> 
> was the same than the output of
> 
> strsplit("3:4", split = c(":"), fixed = TRUE)
> 
> that is, splitting by "," (without effect in this example) and also by ":"
> 
> [[1]]
> [1] "3" "4"
> 
> But, instead, I get
> [[1]]
> [1] "3:4"
> 
> Am I wrongly understanding the help? Is it an expected output?
> I tried with R 3.6.1 for Windows (10).

Yes, you are misunderstanding the help.  Your input x has length 1, so 
only the first element of split will be used.  If you wanted to use 
both, you would need a longer x.  For example,

 > strsplit(c("1:2", "3:4"), split=c(",", ":"), fixed=TRUE)
[[1]]
[1] "1:2"

[[2]]
[1] "3" "4"

The first element is split using "," -- since there are none, there's no 
splitting done.  The second element is split using ":".

Duncan Murdoch