On Jul 23, 2010, at 12:04 PM, stephen sefick wrote:
If you have a zoo series this should work. If it doesn't then please
tell me because I think it works.
snap2min <- function(zoo, min="00:15:00"){
min15 <- times(min)
a <- aggregate(zoo, trunc(time(zoo), min15), function(x) mean(x,
na.rm=TRUE))
}
This "works" for producing 10 half-hour intervals of EDT times:
as.POSIXct(60*30*( round( as.numeric( Sys.time()+
60*30*(1:10))/ # the sequence creation
(60*30))) - # divide prior to rounding
5*60*60, # the TZ offset
origin="1970-01-01" )
[1] "2010-07-23 12:30:00 EDT" "2010-07-23 13:00:00 EDT"
[3] "2010-07-23 13:30:00 EDT" "2010-07-23 14:00:00 EDT"
[5] "2010-07-23 14:30:00 EDT" "2010-07-23 15:00:00 EDT"
[7] "2010-07-23 15:30:00 EDT" "2010-07-23 16:00:00 EDT"
[9] "2010-07-23 16:30:00 EDT" "2010-07-23 17:00:00 EDT"
hth
Stephen Sefick
On Fri, Jul 23, 2010 at 11:00 AM, David Winsemius
<dwinsem...@comcast.net> wrote:
On Jul 23, 2010, at 11:35 AM, David Winsemius wrote:
On Jul 23, 2010, at 11:20 AM, <murali.me...@avivainvestors.com>
<murali.me...@avivainvestors.com> wrote:
Hi folks,
I've got a POSIXct datum as follows:
Sys.time()
[1] "2010-07-23 11:29:59 BST"
I want to convert this to the nearest half-hour, i.e., to
"2010-07-23
11:30:00 BST"
(If the time were "11:59:ss", I want to convert to "12:00:00").
How to achieve this?
Couldn't you just coerce to numeric, divide by 60(sec)*30(half-hour
minutes), round to integer, multiply by 60*30, coerce to POSIXct?
When I tried my method I see that one also needs to add or subtract
the
proper number of seconds from Universal Time to get the output
formatting
correct. (Probably demonstrates that I do not have the proper
understanding
of the right place to employ a TZ specification.).
David Winsemius, MD
West Hartford, CT
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--
Stephen Sefick
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-K. Mullis
David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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