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

[johannes rara]

Thanks, is the same possible using basic gsub/sub/grep etc. functions?

-J

2010/1/2 Gabor Grothendieck <ggrothendieck at gmail.com>:
> 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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>