[R] Omitting repeated occurrence in a string

[David Winsemius]

On Feb 6, 2013, at 11:24 AM, David Winsemius wrote:

> 
> On Feb 6, 2013, at 8:46 AM, Christofer Bogaso wrote:
> 
>> Hello again,
>> 
>> I was looking for some way on How to delete repeated appearance in a
>> String. Let say I have following string:
>> 
>> Text <- "ahsgdvasgAbcabcsdahj"
>> 
>> Here you see "Abc" appears twice. But I want to keep only 1
>> occurrence. Therefore I need that:
>> 
>> Text_result <- "ahsgdvasgAbcsdahj" (i.e. the first one).
>> 
>> Can somebody help me if it is possible using some R function?
> 
> This is not going to solve all possible variations of this problem, but then you proposed testing suite was rather limited, ... don't you agree?
> 
>> Text <- "ahsgdvasgAbcabcsdahabcj"
>> gsub("(abc).*(abc)", "\\1", Text, ignore.case=TRUE)
> [1] "ahsgdvasgAbcj"
> 

This gives some further variations:

> Text <- "ahsgdvasgAbcabcsdahabcj"  #adding a third instance
> gsub("(abc).*(abc)", "\\1", Text, ignore.case=TRUE)
[1] "ahsgdvasgAbcj"
# The first strategy deletes everything  up to and through the last 'abc'


> gsub("(abc)((.*)(abc))", "\\1\\2", Text, ignore.case=TRUE)
[1] "ahsgdvasgAbcabcsdahabcj"
# embedded parenthesies don't seem to "work"

> gsub("(abc)(abc)", "\\1", Text, ignore.case=TRUE)
[1] "ahsgdvasgAbcsdahabcj"
Gets rid of first of sequential instances only.


> Text
[1] "ahsgdvasgAbcabcsdahabcj"
> gsub("(abc)(.?)(abc)", "\\1\\2", Text, ignore.case=TRUE)
[1] "ahsgdvasgAbcsdahabcj"
# Only gets rid of first repeat
> 
#This gets rid of all of sequential repeats but not separated ones
> Text <- "ahsgdvasgAbcabcabcabcabcsdahabcj"
> gsub("(abc)(abc)*", "\\1", Text, ignore.case=TRUE)
[1] "ahsgdvasgAbcsdahabcj"


> 
> 
> -- 
> David Winsemius
> Alameda, CA, USA
> 
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David Winsemius
Alameda, CA, USA