Hi Stefano
I think either of these does what you need...
1: This gets the interval column as you want it, but utilises the lubridate
package:
library(lubridate)
mydf$interval = ceiling_date(mydf$data_POSIX, unit="30 minutes”)
2: Alternative in base R is a bit more long winded: convert the date to numeric
(in seconds), divide by 1800 (seconds in 30min), take the ceiling, and convert
back.
mydf$interval = as.POSIXct(ceiling(as.numeric(mydf$data_POSIX)/1800)*1800,
origin="1970-01-01", tz="Etc/GMT-1")
Cheers
> On 2 Dec 2020, at 17:53, Stefano Sofia <stefano.so...@regione.marche.it>
> wrote:
>
> init_day <- as.POSIXct("2018-02-01-00-00", format="%Y-%m-%d-%H-%M",
> tz="Etc/GMT-1")
> fin_day <- as.POSIXct("2018-02-01-02-00", format="%Y-%m-%d-%H-%M",
> tz="Etc/GMT-1")
> mydf <- data.frame(data_POSIX=seq(init_day, fin_day, by="10 mins"))
> mydf$vmax <- round(rnorm(13, 35, 10))
> mydf$interval <- cut(mydf$data_POSIX, , breaks="30 min")
> means <- aggregate(vmax ~ interval, mydf, mean)
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