[R] Reading and converting time data via read.table

[Jeff Newmiller]

The canonical way to store times is as difftime vectors.  However, there is no simple way to import e.g. HH:MM data directly into such vectors, so you need to embed such times into a longer string that includes a fixed date. After conversion to POSIXct you can subtract the fixed date to get the difftime values.

It is also possible to let the conversion to POSIXct pick "today" by default, but you can sometimes get into trouble if you subtract out "today" on a different day, so I wouldn't recommend it. 

You also may encounter difficulty with daylight savings in this process... but that usually requires knowing a bit more about your data, and if you are already working with time only data you may not be able to fix such problems anyway. 
-- 
Sent from my phone. Please excuse my brevity.

On June 8, 2016 10:20:38 AM PDT, "MacQueen, Don" <macqueen1 at llnl.gov> wrote:
>As far as I know, base R does not have a class for storing times that
>are
>not associated with a date, and recognizing that they are times. That
>being the case, I don't think there is a way to convert them to some
>sort
>of time class while reading them into R using read.table(). I would
>read
>them into R as character strings, and then convert them (it would take
>only a few extra lines of code). How you convert them depends on the
>next
>question, which is:
>
>What do you need to do with those times?
>
>For example, are T1 and T2 the times associated with two events that
>both
>occurred on the specified Date? If that is the case, I would probably
>form
>two POSIXct variables by combining the Date with T1 and the Date with
>T2.
>Or, do you just need to be able to sort your data by T1, or by T2? Or
>do
>you need to calculate the time differences (such as T2-T1) to get the
>number of minutes between those two times?
>
>-Don
>
>-- 
>Don MacQueen
>
>Lawrence Livermore National Laboratory
>7000 East Ave., L-627
>Livermore, CA 94550
>925-423-1062
>
>
>
>
>
>On 6/5/16, 5:53 AM, "R-help on behalf of Ek Esawi"
><r-help-bounces at r-project.org on behalf of esawiek at gmail.com> wrote:
>
>>Hi All--
>>
>>
>>
>>I am relatively new to R. I am reading a csv file via read.table
>(MyFile).
>>The data types in the file are date, string, integer, and time. I was
>able
>>to read all the data and manipulated correctly except time, e.g.,
>12:30. I
>>used as.Date to convert date and string and integer were easily done.
>I
>>could not figure out how to convert the time data correctly. I tried
>chron
>>but w/o success and I read that POSIXlt and POSIXct work only for date
>and
>>time (e.g. 01/02/1999, 12:30:20). I did not try the lubridate package.
>Is
>>there a way to read time data without date attached to it like mine?
>>
>>
>>
>>I am grateful for any help and thanks in advance‹EKE
>>
>>
>>
>>Here is an example of my data when read into R via read.table
>>
>>
>>
>>                AA          Date         Name     T1          T2
>>N1
>>
>>1              312171  7/1/1995       OF      13:37      1:43        
>123
>>
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>>
>>______________________________________________
>>R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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>>PLEASE do read the posting guide
>>http://www.R-project.org/posting-guide.html
>>and provide commented, minimal, self-contained, reproducible code.
>
>______________________________________________
>R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>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.

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