R help - Dec 2007 - strsplit on comma, with a trailing comma in input

I have a comma-separated data file in which trailing commas sometimes occur. 
I am using strsplit to extract the data from this file, and it seems great
except in cases with trailing comma characters.

The example below illustrates.  What I'd like is to get a fourth element in
the answer, being an empty string just like the second element.  Is there a
way I can express my patter (or perhaps specify perl or extended) to get
that?

> strsplit("a,,b,", ",")[[1]]
[1] "a" ""  "b"



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my understanding is that this behavior is known (the help file  
mentions something along these lines in the example).

i'd use something like:

theText <- "a,,b,"
theText <- gsub("\\,$", ", ", theText)

and then use strsplit() on "theText"

b

On Dec 3, 2007, at 6:22 PM, dankelley wrote:
>
> I have a comma-separated data file in which trailing commas  
> sometimes occur.
> I am using strsplit to extract the data from this file, and it seems  
> great
> except in cases with trailing comma characters.
>
> The example below illustrates.  What I'd like is to get a fourth  
> element in
> the answer, being an empty string just like the second element.  Is  
> there a
> way I can express my patter (or perhaps specify perl or extended) to  
> get
> that?
>
>
>> strsplit("a,,b,", ",")[[1]]
> [1] "a" ""  "b"
>
>
>
> -- 
> View this message in context:
http://www.nabble.com/strsplit-on-comma%2C-with-a-trailing-comma-in-input-tf4940023.html#a14141151
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> 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.

Try appending another comma:

strsplit(paste("a,,b,", ",", sep = ""),
",")


On Dec 3, 2007 6:22 PM, dankelley <Dan.Kelley at dal.ca>
wrote:
>
> I have a comma-separated data file in which trailing commas sometimes
occur.
> I am using strsplit to extract the data from this file, and it seems great
> except in cases with trailing comma characters.
>
> The example below illustrates.  What I'd like is to get a fourth
element in
> the answer, being an empty string just like the second element.  Is there a
> way I can express my patter (or perhaps specify perl or extended) to get
> that?
>
>
> > strsplit("a,,b,", ",")[[1]]
> [1] "a" ""  "b"
>
>
>
> --
> View this message in context:
http://www.nabble.com/strsplit-on-comma%2C-with-a-trailing-comma-in-input-tf4940023.html#a14141151
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> 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.
>

dankelley wrote:
> I have a comma-separated data file in which trailing commas sometimes
occur.
> I am using strsplit to extract the data from this file, and it seems great
> except in cases with trailing comma characters.
>
> The example below illustrates.  What I'd like is to get a fourth
element in
> the answer, being an empty string just like the second element.  Is there a
> way I can express my patter (or perhaps specify perl or extended) to get
> that?
>
>
>   
>> strsplit("a,,b,", ",")[[1]]
>>     
> [1] "a" ""  "b"
>   
Hmm, I don't think strsplit can do that. However:

 > scan(textConnection("a,,b,"), sep=",",
what="")
Read 4 items
[1] "a" ""  "b" ""

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