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Counting the occurences of a charater within a string

8 messages · Douglas Esneault, Florent D., Bert Gunter +2 more

#
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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#
## It's not a data frame -- it's just a vector.
[1] "abc/def"     "ghi/jkl/mno"
[1] "/"  "//"
[1] 1 2
?gsub
?nchar

-- Bert

On Thu, Dec 1, 2011 at 8:32 AM, Douglas Esneault
<Douglas.Esneault at mecglobal.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:
#
Resending my code, not sure why the linebreaks got eaten:
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:
#
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:

  
    
#
Inefficient, maybe, but what you suggest does not work if a string
starts or ends with a slash.
On Thu, Dec 1, 2011 at 11:11 PM, Bert Gunter <gunter.berton at gene.com> wrote:
#
On Dec 1, 2011, at 11:11 PM, Bert Gunter wrote:

            
Definitely more compact that the regex alternates I came up with, but  
one of these still might appeal in situations where it was desireable  
to have the source strings as labels:

 > sapply( sapply(x$Col1, gregexpr, patt="/"), length)
     abc/def ghi/jkl/mno
           1           2

 > nchar( sapply(x$Col1, gsub, patt="[^/]", rep="" ) )
     abc/def ghi/jkl/mno
           1           2
1 day later
#
On Thu, Dec 1, 2011 at 10:32 AM, Douglas Esneault
<Douglas.Esneault at mecglobal.com> wrote:
Here's an easy way from stringr:

library(stringr)
str_count( c("abc/def", "ghi/jkl/mno"), "/")
# [1] 1 2

Hadley