[R] what is the faster way to search for a pattern in a few million entries data frame ?

[Jim Lemon]

Hi Fabien,
I was going to send this last night, but I thought it was too simple.
Runs in about one millisecond.

df<-data.frame(freq=runif(1000),
 strings=apply(matrix(sample(LETTERS,10000,TRUE),ncol=10),
 1,paste,collapse=""))
match.ind<-grep("DF",df$strings)
match.ind
 [1]   2  11  91 133 169 444 547 605 734 943

Jim


On Mon, Apr 11, 2016 at 5:27 AM, Fabien Tarrade
<fabien.tarrade at gmail.com> wrote:
> Hi Duncan,
>>
>> Didn't you post the same question yesterday?  Perhaps nobody answered
>> because your question is unanswerable.
>
> sorry, I got a email that my message was waiting for approval and when I
> look at the forum I didn't see my message and this is why  I sent it again
> and this time I did check that the format of my message was text only. Sorry
> for the noise.
>>
>> You need to describe what the strings are like and what the patterns are
>> like if you want advice on speeding things up.
>
> my strings are 1-gram up to 5-grams (sequence of 1 work up to 5 words) and I
> am searching for the frequency in my DF of the strings starting with a
> sequence of few words.
>
> I guess these days it is standard to use DF with millions of entries so I
> was wondering how people are doing that in the faster way.
>
> Thanks
> Cheers
> Fabien
>
> --
> Dr Fabien Tarrade
>
> Quantitative Analyst/Developer - Data Scientist
>
> Senior data analyst specialised in the modelling, processing and statistical
> treatment of data.
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>
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