Re: [Rd] (PR#8777) strsplit does [not] return correct value when spliting ""

From: Peter Ehlers <ehlers_at_math.ucalgary.ca>
Date: Mon 17 Apr 2006 - 21:02:43 GMT

Charles,

Can't you achieve your goal by unlist()ing 'substrings'?

  max(nchar(unlist(substrings)))

Peter Ehlers

Charles Dupont wrote:
> Now using R 2.3.0.
>
> I have a string that can be "". I want to find the max screen width of
> the all the lines in the string. so I run the command
>
> > x <- c("hello", "bob is\ngreat", "foo", "", "bar")
> > substrings <- strsplit(x, "\n"), type="width")
> > sapply(substrings, FUN=function(x) max(nchar(x, type="width")))
> which returns
> [1] 5 6 3 -Inf 3
>
> This happens because of the behavior of strsplit for a string that is not ""
> > strsplit("Hello\nBob", "\n")
>
> it returns
> [[1]]
> [1] "Hello" "Bob"
>
>
> for a string that is ""
> > strsplit("", "\n")
>
> it returns
> [[1]]
> character(0)
>
>
> I would expect
> [[1]]
> [1] ""
>
> because "" is character vector of length 1 containing a string of length
> 0, not a character vector of length 0.
>
> For any other string if the split string is not matched in argument x
> then it returns the original string x.
>
> The man page states in the value section that strsplit returns:
> A list of length 'length(x)' the 'i'-th element of which contains
> the vector of splits of 'x[i]'.
>
> It mentions no change in behavior if the value of x[i] = "".
>
> Prof Brian Ripley wrote:
>

>>Please use a current version of R: we are at 2.3.0RC (and we do ask you 
>>not to report on obselete versions).
>>
>>What rule are you using, and where did you find it in the R documentation?
>>
>>In fact
>>
>>
>>>strsplit("", " ")
>>
>>[[1]]
>>character(0)
>>
>>which is not as you stated.   This is a feature, as it distinct from
>>
>>
>>>strsplit(" ", " ")
>>
>>[[1]]
>>[1] ""
>>
>>Consider also
>>
>>
>>>strsplit("", "")
>>
>>[[1]]
>>character(0)
>>
>>
>>>strsplit("a", "")
>>
>>[[1]]
>>[1] "a"
>>
>>
>>>strsplit("ab", "")
>>
>>[[1]]
>>[1] "a" "b"
>>
>>
>>On Mon, 17 Apr 2006, charles.dupont@vanderbilt.edu wrote:
>>
>>
>>>Full_Name: Charles Dupont
>>>Version: 2.2.0
>>>OS: linux
>>>Submission from: (NULL) (160.129.129.136)
>>>
>>>
>>>when
>>>
>>>strsplit("", " ")
>>>
>>>returns character(0)
>>>
>>>where as
>>>
>>>strsplit("a", " ")
>>>
>>>returns "a".
>>>
>>>these return values are not constiant with each other.
>>>
>>>Charles Dupont
>>>
>>>______________________________________________
>>>R-devel@r-project.org mailing list
>>>https://stat.ethz.ch/mailman/listinfo/r-devel
>>>
>>>
>>

>

>

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https://stat.ethz.ch/mailman/listinfo/r-devel Received on Tue Apr 18 07:05:39 2006

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