[R] cumulative time durations of specified periods (chron)

[Sebastian Luque]

On Tue, 13 Jun 2006 18:49:09 -0700,
Spencer Graves <spencer.graves at pdf.com> wrote:

	  > Did you try the following:
>
>> xto-xfrom
> Time in days:
> [1] 1.50 1.75 2.00 2.25
>
	  Also, have you seen Gabor Grothendieck and Thomas Petzoldt. "R
help desk: Date and time classes in R". R News, 4(1):29-32, June 2004.,
downloadable from www.r-project.org -> "Documentation:  Newsletter" as
well as the "zoo" vignette (see
"http://finzi.psych.upenn.edu/R/Rhelp02a/archive/67006.html")?
>
> 	  hope this helps.
> 	  Spencer Graves
>
> Sebastian Luque wrote:
>> Hi,
>> Say we have two chron vectors representing start and end date/times of
>> an
>> event, respectively:
>> R> (xfrom <- chron(seq(1.25, 11, 3.25)))
>> [1] (01/02/70 06:00:00) (01/05/70 12:00:00) (01/08/70 18:00:00)
>> [4] (01/12/70 00:00:00)
>> R> (xto <- chron(as.numeric(xfrom) + seq(1.5, 2.25, 0.25)))
>> [1] (01/03/70 18:00:00) (01/07/70 06:00:00) (01/10/70 18:00:00)
>> [4] (01/14/70 06:00:00)
>> and we would like to know how much time is included in a number of
>> intervals within each event.  We can define the intervals with two chron
>> vectors:
>> R> (xt0 <- times(c(0.50, 0)))
>> [1] 12:00:00 00:00:00
>> R> (xt1 <- times(c(1 - (1 / 86400), 0.25)))
>> [1] 23:59:59 06:00:00
>> So for the first event, 01/02/70 06:00:00 to 01/03/70 18:00:00, the
>> interest is to find how much time corresponds to periods 12:00:00 -
>> 23:59:59 and 00:00:00 - 06:00:00.
>> I began writing a function to accomplish this task, but am at an
>> impasse.
>> The archives may have something on this, but I haven't found a good search
>> query for it, so I'd appreciate some pointers.  Thanks in advance.
>> Cheers,
>>

-- 
Sebastian P. Luque                    Current address:
Department of Biology                 Fisheries and Oceans Canada
Memorial University of Newfoundland   501 University Crescent
sluque at mun.ca                         Winnipeg, MB R3T 2N6, Canada
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