[R] Fast string comparison

[Hadley Wickham]

strings <- replicate(1e5, paste(sample(letters, 100, rep = T), collapse =  ""))
system.time(strings[-1] == strings[-1e5])
#   user  system elapsed
#  0.016   0.000   0.017

So it takes ~1/100 of a second to do ~100,000 string comparisons. You
need to provide a reproducible example that illustrates why you think
string comparisons are slow.

Hadley


On Tue, Jul 13, 2010 at 6:52 AM, Ralf B <ralf.bierig at gmail.com> wrote:
> I am asking this question because String comparison in R seems to be
> awfully slow (based on profiling results) and I wonder if perhaps '=='
> alone is not the best one can do. I did not ask for anything
> particular and I don't think I need to provide a self-contained source
> example for the question. So, to re-phrase my question, are there more
> (runtime) effective ways to find out if two strings (about 100-150
> characters long) are equal?
>
> Ralf
>
>
>
>
>
>
> On Sun, Jul 11, 2010 at 2:37 PM, Sharpie <chuck at sharpsteen.net> wrote:
>>
>>
>> Ralf B wrote:
>>>
>>> What is the fastest way to compare two strings in R?
>>>
>>> Ralf
>>>
>>
>> Which way is not fast enough?
>>
>> In other words, are you asking this question because profiling showed one of
>> R's string comparison operations is causing a massive bottleneck in your
>> code? If so, which one and how are you using it?
>>
>> -Charlie
>>
>> -----
>> Charlie Sharpsteen
>> Undergraduate-- Environmental Resources Engineering
>> Humboldt State University
>> --
>> View this message in context: http://r.789695.n4.nabble.com/Fast-string-comparison-tp2285156p2285409.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
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>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/