[R] converting a time to nearest half-hour
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? Thanks, Murali __ R-help@r-project.org mailing list 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.
Re: [R] converting a time to nearest half-hour
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? _ David Winsemius, MD West Hartford, CT __ R-help@r-project.org mailing list 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.
Re: [R] converting a time to nearest half-hour
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 __ R-help@r-project.org mailing list 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.
Re: [R] converting a time to nearest half-hour
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))
}
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
__
R-help@r-project.org mailing list
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.
--
Stephen Sefick
| Auburn University |
| Department of Biological Sciences |
| 331 Funchess Hall |
| Auburn, Alabama |
| 36849 |
|___|
| sas0...@auburn.edu |
| http://www.auburn.edu/~sas0025 |
|___|
Let's not spend our time and resources thinking about things that are
so little or so large that all they really do for us is puff us up and
make us feel like gods. We are mammals, and have not exhausted the
annoying little problems of being mammals.
-K. Mullis
__
R-help@r-project.org mailing list
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.
Re: [R] converting a time to nearest half-hour
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
__
R-help@r-project.org mailing list
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.
--
Stephen Sefick
| Auburn University |
| Department of Biological Sciences |
| 331 Funchess Hall |
| Auburn, Alabama |
| 36849|
|___|
| sas0...@auburn.edu |
| http://www.auburn.edu/~sas0025 |
|___|
Let's not spend our time and resources thinking about things that are
so little or so large that all they really do for us is puff us up and
make us feel like gods. We are mammals, and have not exhausted the
annoying little problems of being mammals.
-K. Mullis
David Winsemius, MD
West Hartford, CT
__
R-help@r-project.org mailing list
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.
Re: [R] converting a time to nearest half-hour
By entering trunc.POSIXt at the R commandline, you can see the standard
truncate implementation. Riffing on this,
roundhalfhour - function( x ) {
x - as.POSIXlt( x + as.difftime( 15, units=mins ) )
x$sec - 0
x$min - 30*(x$min %/% 30)
as.POSIXct(x)
}
The as.double approach ought to work also, but rounding error might be a
problem.
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
__
R-help@r-project.org mailing list
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.
---
Jeff NewmillerThe . . Go Live...
DCN:jdnew...@dcn.davis.ca.usBasics: ##.#. ##.#. Live Go...
Live: OO#.. Dead: OO#.. Playing
Research Engineer (Solar/BatteriesO.O#. #.O#. with
/Software/Embedded Controllers) .OO#. .OO#. rocks...1k
---
Sent from my phone. Please excuse my brevity.
__
R-help@r-project.org mailing list
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.
Re: [R] converting a time to nearest half-hour
This truncates to quarter-hour rather than rounding to half-hour.
stephen sefick ssef...@gmail.com 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))
}
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
__
R-help@r-project.org mailing list
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.
--
Stephen Sefick
| Auburn University |
| Department of Biological Sciences |
| 331 Funchess Hall |
| Auburn, Alabama |
| 36849 |
|___|
| sas0...@auburn.edu |
| http://www.auburn.edu/~sas0025 |
|___|
Let's not spend our time and resources thinking about things that are
so little or so large that all they really do for us is puff us up and
make us feel like gods. We are mammals, and have not exhausted the
annoying little problems of being mammals.
-K. Mullis
__
R-help@r-project.org mailing list
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.
---
Jeff NewmillerThe . . Go Live...
DCN:jdnew...@dcn.davis.ca.usBasics: ##.#. ##.#. Live Go...
Live: OO#.. Dead: OO#.. Playing
Research Engineer (Solar/BatteriesO.O#. #.O#. with
/Software/Embedded Controllers) .OO#. .OO#. rocks...1k
---
Sent from my phone. Please excuse my brevity.
__
R-help@r-project.org mailing list
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.
Re: [R] converting a time to nearest half-hour
The arithmetic that David describes should work fine (POSIXct is internally in UTC) unless you are in the Chatham Islands (which has a UTC+12:45 time zone [1]) or Nepal (UTC+05:45 [2]) or some such place with a funny idea about when the 1/2 hour mark is. The formatting of the output may be tricky, if the original poster really want the (past/future) time zone as opposed to the current one, which is what his text could be read to suggest. Good test cases would be 2010-03-28 01:46:00 GMT which should (presumably) round to 2010-03-28 03:00:00 BST and 2010-10-31 02:46 BST which probably rounds to 2010-10-31 02:00 GMT. I can't quite get it to work in R, but it should be possible Allan [1] https://secure.wikimedia.org/wikipedia/en/wiki/UTC%2B12:45 [2] https://secure.wikimedia.org/wikipedia/en/wiki/UTC%2B05:45 On 23/07/10 16:35, 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? _ David Winsemius, MD West Hartford, CT __ R-help@r-project.org mailing list 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.
Re: [R] converting a time to nearest half-hour
David, Stephen,
You're right - it's the time zone conventions that threw me as well. I tried
those round() operations earlier, but inevitably ended up being either an hour
behind. Even when I specified my time zone, it didn't make any difference. So
there's something else that I'm missing. I'll take a look at your various
approaches, and get back to you.
Cheers,
Murali
-Original Message-
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
Behalf Of David Winsemius
Sent: 23 July 2010 17:15
To: stephen sefick
Cc: r-help@r-project.org
Subject: Re: [R] converting a time to nearest half-hour
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
__
R-help@r-project.org mailing list
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.
--
Stephen Sefick
| Auburn University |
| Department of Biological Sciences |
| 331 Funchess Hall |
| Auburn, Alabama |
| 36849|
|___|
| sas0...@auburn.edu |
| http://www.auburn.edu/~sas0025 |
|___|
Let's not spend our time and resources thinking about things that are
so little or so large that all they really do for us is puff us up and
make us feel like gods. We are mammals, and have not exhausted the
annoying little problems of being mammals.
-K. Mullis
David Winsemius, MD
West Hartford, CT
__
R-help@r-project.org mailing list
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.
__
R-help@r-project.org mailing list
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.
Re: [R] converting a time to nearest half-hour
On Fri, Jul 23, 2010 at 12:35 PM, murali.me...@avivainvestors.com wrote: David, Stephen, You're right - it's the time zone conventions that threw me as well. I tried those round() operations earlier, but inevitably ended up being either an hour behind. Even when I specified my time zone, it didn't make any difference. So there's something else that I'm missing. I'll take a look at your various approaches, and get back to you. Does your problem really involve time zones? If not you would likely be best off using a datetime class that has no time zone so you don't run into this problem in the first place. Also its particularly easy with chron due to the availability of trunc.times() : library(chron) now - as.chron(format(Sys.time())) trunc(now + as.numeric(times(00:15:00)), 00:30:00) With POSIXct you could muck with the internals like this (which uses the fact that there are 1800 seconds in an half hour): x - Sys.time() structure(1800 * (as.numeric(x + 900) %/% 1800), class = class(x)) See the article in R News 4/1 for more. __ R-help@r-project.org mailing list 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.
