aggregate semi-hourly data not 00-24 but 9-9

Inviato: marted? 22 settembre 2020 11.00
A: Jeff Newmiller
Cc: Stefano Sofia; r-help mailing list
Oggetto: Re: [R] aggregate semi-hourly data not 00-24 but 9-9

Thanks Jeff.
Stefano, per Jeff's comment, you can replace the line

df1$data_POSIXminus9 <- df1$data_POSIX - lubridate::hours(9)

by

df1$data_POSIXminus9 <- df1$data_POSIX - as.difftime(9,units="hours")

On Mon, Sep 21, 2020 at 8:06 PM Jeff Newmiller <jdnewmil at dcn.davis.ca.us> wrote:
>
> The base R as.difftime function is perfectly usable to create this offset without pulling in lubridate.
>
> On September 21, 2020 8:06:51 AM PDT, Eric Berger <ericjberger at gmail.com> wrote:
> >Hi Stefano,
> >If you mean from 9am on one day to 9am on the following day, you can
> >do a trick. Simply subtract 9hrs from each timestamp and then you want
> >midnight to midnight for these adjusted times, which you can get using
> >the method you followed.
> >
> >I googled and found that lubridate::hours() can be used to add or
> >subtract hours from a POSIXct.
> >
> >library(lubridate)
> >
> >day_1 <- as.POSIXct("2020-02-19-00-00", format="%Y-%m-%d-%H-%M",
> >tz="Etc/GMT-1")
> >day_2 <- as.POSIXct("2020-02-24-12-00", format="%Y-%m-%d-%H-%M",
> >tz="Etc/GMT-1")
> >df1 <- data.frame(data_POSIX=seq(day_1, day_2, by="30 min"))
> >df1$hs <- rnorm(nrow(df1), 40, 10)
> >df1$diff[2:nrow(df1)] <- diff(df1$hs)
> >
> >df1$data_POSIXminus9 <- df1$data_POSIX - lubridate::hours(9)
> >df1$dayX <- format(df1$data_POSIXminus9,"%y-%m-%d")
> >df2X <- aggregate(diff ~ dayX, df1, sum)
> >df2X
> >
> >HTH,
> >Eric
> >
> >On Mon, Sep 21, 2020 at 5:30 PM Stefano Sofia
> ><stefano.sofia at regione.marche.it> wrote:
> >>
> >> Dear R-list members,
> >> I have semi-hourly snowfall data.
> >> I should sum the semi-hourly increments (only the positive ones, but
> >this is not described in my example) day by day, not from 00 to 24 but
> >from 9 to 9.
> >>
> >> I am able to use the diff function, create a list of days and use the
> >function aggregate, but it works only from 0 to 24. Any suggestion for
> >an efficient way to do it?
> >> Here my code:
> >> day_1 <- as.POSIXct("2020-02-19-00-00", format="%Y-%m-%d-%H-%M",
> >tz="Etc/GMT-1")
> >> day_2 <- as.POSIXct("2020-02-24-12-00", format="%Y-%m-%d-%H-%M",
> >tz="Etc/GMT-1")
> >> df1 <- data.frame(data_POSIX=seq(day_1, day_2, by="30 min"))
> >> df1$hs <- rnorm(nrows(df1), 40, 10)
> >> df1$diff[2:nrow(df1)] <- diff(df1$hs)
> >> df1$day <- format(df$data_POSIX,"%y-%m-%d")
> >> df2 <- aggregate(diff ~ day, df, sum)
> >>
> >> Thank you for your help
> >> Stefano
> >>
> >>          (oo)
> >> --oOO--( )--OOo----------------
> >> Stefano Sofia PhD
> >> Civil Protection - Marche Region
> >> Meteo Section
> >> Snow Section
> >> Via del Colle Ameno 5
> >> 60126 Torrette di Ancona, Ancona
> >> Uff: 071 806 7743
> >> E-mail: stefano.sofia at regione.marche.it
> >> ---Oo---------oO----------------
> >>
> >> ________________________________
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IMPORTANT NOTICE: This e-mail message is intended to be received only by persons entitled to receive the confidential information it may contain. E-mail messages to clients of Regione Marche may contain information that is confidential and legally privileged. Please do not read, copy, forward, or store this message unless you are an intended recipient of it. If you have received this message in error, please forward it to the sender and delete it completely from your computer system.

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