[R] Regexp: extract first occurrence of date in string

[Gabor Grothendieck]

Try this which uses a slightly simpler regexp:

> library(gsubfn)
> strapply(txt, "(\\d{1,2}\\.\\d{1,2}\\.\\d{4}).*")[[1]]
[1] "05.12.2009"

or we could convert it to Date class at the same time where we have
assumed month.day.year:

> strapply(txt, "(\\d{1,2}\\.\\d{1,2}\\.\\d{4}).*", ~ as.Date(x, "%m.%d.%Y"))[[1]]
[1] "2009-05-12"

or this even simpler regexp extracting all the dates and then picking
off the first:

> strapply(txt, "\\d{1,2}\\.\\d{1,2}\\.\\d{4}")[[1]][1]
[1] "05.12.2009"

On Sat, Jan 2, 2010 at 10:08 AM, johannes rara <johannesraja at gmail.com> wrote:
> I would like to extract first date from a string:
>
>> txt <- "first date is 05.12.2009. Second date is 06.12.2009."
>> txt
> [1] "first date is 05.12.2009. Second date is 06.12.2009."
>
> I tried:
>
>> sub("^.*?\\s(\\d{1,2}\\.\\d{1,2}\\.\\d{4})", "\\1", txt, extended=T, perl=T)
> [1] "05.12.2009. Second date is 06.12.2009."
>>
>
> How to modify this?
>
> -J
>
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