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

[Spencer Graves]

	  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,
>