[R] Sum per hour

[Gabor Grothendieck]

We could do it using either POSIXct or chron:

library(zoo)

# POSIXct
z <- zoo(precipitation, as.POSIXct(time, tz = "GMT"))
aggregate(z, function(x) as.POSIXct(trunc(x, "hour")), sum)

# chron
library(chron)
z <- zoo(precipitation, as.chron(as.POSIXct(time, tz = "GMT"))
aggregate(z, function(x) chron(trunc(times(x), "01:00:00")), sum)


On 5/24/07, jessica.gervais at tudor.lu <jessica.gervais at tudor.lu> wrote:
>
> Dear all,
>
> I have a list of precipitation record and a list of time
> I would like to sum them up per hour, or per day.
> Does such a function exist ?
>
>
> example:
> time<-c("2000-10-03 14:00:00","2000-10-03 14:10:00","2000-10-03
> 14:20:00","2000-10-03 15:30:00","2000-10-03 16:40:00","2000-10-03
> 16:50:00","2000-10-03 17:00:00","2000-10-03 17:10:00","2000-10-03
> 17:20:00","2000-10-03 18:30:00","2000-10-04 14:00:00","2000-10-04
> 14:10:00","2000-10-04 14:20:00","2000-10-04 15:30:00","2000-10-04
> 16:40:00","2000-10-04 16:50:00","2000-10-04 17:00:00","2000-10-04
> 17:10:00","2000-10-04 17:20:00","2000-10-04 18:30:00")
>
> precipitation<-c(0,0.1,0,0,0,0,0.2,0.3,0.5,6,7,8,9,1,0,0,0,0,1,0)
>
> DATA<-cbind(time,precipitation)
>
> ... ?
> how to sum up per hour ?
>
> Thanks in advance
>
> Jessica
>
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