[R] Counting the occurences of a charater within a string

[Bert Gunter]

strsplit is certainly an alternative, but your approach is
unnecessarily complicated and inefficient. Do this, instead:

sapply(strsplit(x,"/"),length)-1

Cheers,
Bert

On Thu, Dec 1, 2011 at 7:44 PM, Florent D. <flodel at gmail.com> wrote:
> Resending my code, not sure why the linebreaks got eaten:
>
>> x <- data.frame(Col1 = c("abc/def", "ghi/jkl/mno"), stringsAsFactors = FALSE)
>> count.slashes <- function(string)sum(unlist(strsplit(string, NULL)) == "/")
>> within(x, Col2 <- vapply(Col1, count.slashes, 1))
>         Col1 Col2
> 1     abc/def    1
> 2 ghi/jkl/mno    2
>
>
> On Thu, Dec 1, 2011 at 10:32 PM, Florent D. <flodel at gmail.com> wrote:
>> I used within and vapply:
>>
>> x <- data.frame(Col1 = c("abc/def", "ghi/jkl/mno"), stringsAsFactors = FALSE)
>> count.slashes <- function(string)sum(unlist(strsplit(string, NULL)) ==
>> "/")within(x, Col2 <- vapply(Col1, count.slashes, 1))
>>          Col1 Col21     abc/def    12 ghi/jkl/mno    2
>>
>> On Thu, Dec 1, 2011 at 1:05 PM, Bert Gunter <gunter.berton at gene.com> wrote:
>>> ## It's not a data frame -- it's just a vector.
>>>
>>>> x
>>> [1] "abc/def"     "ghi/jkl/mno"
>>>> gsub("[^/]","",x)
>>> [1] "/"  "//"
>>>> nchar(gsub("[^/]","",x))
>>> [1] 1 2
>>>>
>>>
>>> ?gsub
>>> ?nchar
>>>
>>> -- Bert
>>>
>>> On Thu, Dec 1, 2011 at 8:32 AM, Douglas Esneault
>>> <Douglas.Esneault at mecglobal.com> wrote:
>>>> I am new to R but am experienced SAS user and I was hoping to get some help on counting the occurrences of a character within a string at a row level.
>>>>
>>>> My dataframe, x,  is structured as below:
>>>>
>>>> Col1
>>>> abc/def
>>>> ghi/jkl/mno
>>>>
>>>> I found this code on the board but it counts all occurrences of "/" in the dataframe.
>>>>
>>>> chr.pos <- which(unlist(strsplit(x,NULL))=='/')
>>>> chr.count <- length(chr.pos)
>>>> chr.count
>>>> [1] 3
>>>>
>>>> I'd like to append a column, say cnt, that has the count of "/" for each row.
>>>>
>>>> Can anyone point me in the right direction or offer some code to do this?
>>>>
>>>> Thanks in advance for the help.
>>>>
>>>> Doug Esneault
>>>>
>>>>
>>>>
>>>>
>>>>
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>>>
>>>
>>>
>>> --
>>>
>>> Bert Gunter
>>> Genentech Nonclinical Biostatistics
>>>
>>> Internal Contact Info:
>>> Phone: 467-7374
>>> Website:
>>> http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.



-- 

Bert Gunter
Genentech Nonclinical Biostatistics

Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm