Thank you for your help, Michael. I used *aggregate(x, by = timeSequence(by = "day"), FUN = sum)* but the results is very different from *sum(x[1:13])*, where 13 is the number of daily observations I've sampled.
Michael Weylandt wrote > > How are you using aggregate()? It seems to sum for me... > > z <- zoo(1:50, seq.POSIXt(from = Sys.time(), by = "30 min", length.out = > 50)) > > aggregate(z, as.Date(time(z)), sum) > > Best, > Michael > > On Tue, May 15, 2012 at 11:52 AM, Cren <oscar.soppelsa@> wrote: >> Hello, >> >> I have a time series with intraday datas, sampled every 30'; I would need >> to >> aggregate them in this way: summing up all datas within a day. >> >> I tried to use *aggregate(...)* function to get my goal, but it >> aggregates >> in wrong way (I did not understand how so far); what I need is like >> *sum(...)* function applied to datas within the same day. >> >> Thank you :) >> >> -- >> View this message in context: >> http://r.789695.n4.nabble.com/How-to-sum-and-group-data-by-DATE-in-data-frame-tp903708p4630119.html >> Sent from the R help mailing list archive at Nabble.com. >> >> ______________________________________________ >> R-help@ 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@ 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. > -- View this message in context: http://r.789695.n4.nabble.com/How-to-sum-and-group-data-by-DATE-in-data-frame-tp903708p4630139.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.