[R] How to extract information from the following dataset?

[John Kane]

? subset  day = x time > y | time < z

--- On Thu, 5/12/11, hwright <heather.wright at maine.edu> wrote:

> From: hwright <heather.wright at maine.edu>
> Subject: Re: [R] How to extract information from the following dataset?
> To: r-help at r-project.org
> Received: Thursday, May 12, 2011, 6:18 AM
> 
> I have the following data set, in a csv file, looks like
> the following:
> 
> Jan 27, 2010  16:01:24,000 125 - - -
> Jan 27, 2010  16:06:24,000 125 - - -
> ......
> The first few columns are month, day, year, time with OS3
> accuracy. And the
> last number is the measurement I need to extract.
> I wonder if there is a easy way to just take out the
> measurements only from
> a specific day and hour
> -- 
> Xin Zhang
> Ph.D Candidate
> Department of Statistics
> University of California, Riverside
> -------------------------------------------------------------------
> 
> I use strptime to configure the date format in my times
> series dataset.
> First check to see how the dates are read.
> For example:
> # check the structure
> str(your_file)
> 'data.frame' ...etc
> This tells me that my original date is a factor but not in
> POSIXlt format.
> 
> #check your column dates
> head(your_file)
> [1] "1984-01-26" "1984-02-09" "1984-03-01" "1984-03-15"
> "1984-03-29"
> "1984-04-12"
> These are discrete column dates.
> 
> #convert your date format
> your_file$date<- strptime(your_file$date,"%m/%d/%Y")
> call ?strptime for options
> 
> Example:
> For a specific day or hour, strptime would utilize:
> strptime(your_file$date,"%d/%I") for day and hour.
> 
> Once you extract the type of date format you want, run
> str(your_file) again
> to confirm the format change.
> Does this answer your question?
> Best,
> 
> 
> 
> -----
> -------------------------------
> Heather A. Wright, PhD candidate
> Ecology and Evolution of Plankton
> Stazione Zoologica Anton Dohrn
> Villa Comunale
> 80121 - Napoli, Italy
> --
> View this message in context: http://r.789695.n4.nabble.com/How-to-extract-information-from-the-following-dataset-tp3516752p3516952.html
> Sent from the R help mailing list archive at Nabble.com.
> 
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