[R] how to choose dates data?

[Prof Brian Ripley]

On 04/07/2013 08:04, Dante.py wrote:
> I have a method which is not so smart --use grep to match the pattern.
> for example:
> dates <- c("02/27/92", "02/27/92", "01/14/92", "02/28/92", "02/01/91")
> day <- as.Date(dates, "%m/%d/%y")
> day:
> [1] "1992-02-27" "1992-02-27" "1992-01-14" "1992-02-28" "1991-02-01"
> If I want to search for 1991, I can use:
> grep("1991-*", day)
>
>
> Hope for a better solution.

Here are 2.  The first is quite obvious, the second is faster but needs 
more knowledge.

x <- format(day, "%Y")
day[x >= "2007" & x <= "2009"]

x <- as.POSIXlt(day)$year + 1900
day[x >= 2007 & x <= 2009]

>
>
> 2013/7/4 Gallon Li <gallon.li at gmail.com>
>
>> i have converted my data into date format like below:
>>
>>> day=as.Date(originaldate,"%m/%d/%Y")
>>> day[1:5]
>> [1] "2008-04-12" "2011-07-02" "2011-09-02" "2008-04-12" "2008-04-12"
>>
>> I wish to select only those observations from 2007 to 2009, how can I
>> select from this list?
>>
>>          [[alternative HTML version deleted]]
>>
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>>
>
>
>
>
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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