[R] Round down to earliest hour or half hour

[Rui Barradas]

Hello,

See if the following function does it


#----------------------------------------------------------------------
# Round POSIXct date/time
#
round.POSIXct <- function(x, units = c("mins", "5 mins", "10 mins", "15 
mins", "quarter hours", "30 mins", "half hours", "hours")){
	if(is.numeric(units)) units <- as.character(units)
	units <- match.arg(units)
	r <- switch(units,
		"mins" = 60,
		"5 mins" = 60*5,
		"10 mins" = 60*10,
		"15 mins"=, "quarter hours" = 60*15,
		"30 mins"=, "half hours" = 60*30,
		"hours" = 60*60
	)
	H <- as.integer(format(x, "%H")
	M <- as.integer(format(x, "%M"))
	S <- as.integer(format(x, "%S"))
	D <- format(x, "%Y-%m-%d")
	secs <- 3600*H + 60*M + S
	as.POSIXct(round(secs/r)*r, origin=D)
}

(x <- Sys.time() + 1:10*60)
round(x, "5 mins")
round(x, 5)
round(x, "10 mins")
round(x, "quarter")
round(x, "15 mins")


Hope this helps,

Rui Barradas

Em 09-06-2012 03:04, Phil Hurvitz escreveu:
> I wanted to round rather than truncate timestamps
>
> # create a data set to work with
> s <- 30 * rnorm(10, 1, 0.1)
> gps.timestamp <- Sys.time() + s*1:10
> gps.timestamp <- c(round(gps.timestamp[1], "min"), gps.timestamp,
> as.POSIXct("2012-06-08 17:32:59"), as.POSIXct("2012-06-08 17:32:30"))
>
> f <- function(gps.timestamp=gps.timestamp, interval=30){
>      # is the interval a multiple of 60? if so, just round
>      if(interval %% 60 == 0){
>          return(data.frame(gps.timestamp,
> gps.timestamp.round=round(gps.timestamp, "min")))
>      }
>      # a POSIXlt timestamp for fiddling with seconds
>      lt <- as.POSIXlt(gps.timestamp)
>      # extract rounded seconds from the timestamp
>      gps.seconds <- round(lt$sec, 0)
>      # the number of segments in a minute is 60/interval
>      seg <- 60/interval
>      # the cutpoints
>      rounds <- c(0, 1:seg * interval)
>      # the "midpoints" for cutting
>      cuts <- c(-1, 1:seg * 60/seg - interval/2, 60)
>      # and a numeric representation of the cut position
>          # (the factor position, really)
>      numcut <- as.numeric(cut(gps.seconds,cuts))
>      # the rounded seconds (*not* truncated)
>      round.seconds <- rounds[numcut]
>      # truncate the date to the nearest low minute
>      lt <- lt1 <- trunc(lt, "min")
>      # add the rounded seconds to the truncated minutes
>      lt1 <- lt1 + round.seconds
>      # how does that look?
>      return(data.frame(gps.timestamp, gps.timestamp.round=lt1))
> }
>
>
> # try it:
> f(gps.timestamp, 15)
> f(gps.timestamp, 30)
> f(gps.timestamp, 10)
>
> -P.
>
> **************************************************************
> Philip M. Hurvitz, PhD | Research Assistant Professor | UW-CBE
> Urban Form Lab  | 1107 NE 45th Street, Suite 535  | Box 354802
> University of Washington, Seattle, Washington  98195-4802, USA
> phurvitz at u.washington.edu | http://gis.washington.edu/phurvitz
> "What is essential is invisible to the eye." -de Saint-Exupéry
> **************************************************************
>
>> I would use package chron and trunc()....
>>
>> One example from the help of trunc.times (modified):
>>
>> lirary(chron)
>> tt <- times(c("12:13:14", "15:46:17"))
>> trunc(tt, times("00:30:00"))
>>
>>
>> HTH
>> Jannis
>>
>> --- Schatzi <adele_thompson at cargill.com> schrieb am Mo, 9.5.2011:
>>
>>> Von: Schatzi <adele_thompson at cargill.com>
>>> Betreff: [R] Round down to earliest hour or half hour
>>> An: r-help at r-project.org
>>> Datum: Montag, 9. Mai, 2011 14:06 Uhr
>>> I have times and would like to round
>>> down to the earliest 30 minute
>>> increment. For instance, a time of
>>> 2011-04-28 09:02:00
>>> (the as.numeric value = 1303999320)
>>> I would like it to be rounded down to:
>>> 2011-04-28 09:00:00
>>> (the as.numeric value = 1303999200)
>>>
>>> Any ideas of how to do this?
>
> ______________________________________________
> R-help at 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.