An easy way to average every 30 minutes is using the aggregate function. First I use the mod (%%) to get times as the next earliest possible 30 min time increment.
bTime<- as.POSIXct(c( "2011-04-28 09:02:00 CDT","2011-04-28 09:02:00 CDT","2011-04-28 09:12:00 CDT","2011-04-28 09:14:00 CDT","2011-04-28 09:15:00 CDT","2011-04-28 09:23:00 CDT","2011-04-28 09:45:00 CDT","2011-04-28 09:53:00 CDT","2011-04-28 10:03:00 CDT")) numTime<-as.numeric(bTime)-21600 Weight<-runif(9)*100 minT<-30 excess<-numTime %% (minT*60) nTime<-numTime-excess nDateT<-as.POSIXct(nTime, origin="1970-01-01",tz= "US/Central") meanw <- aggregate(Weight, list(nDateT), mean, na.rm = TRUE) -----Original Message----- From: cl...@ecy.wa.gov [mailto:cl...@ecy.wa.gov] Sent: Thursday, May 05, 2011 03:58 PM To: Thompson, Adele - adele_thomp...@cargill.com Cc: r-help@r-project.org Subject: Re: [R] Averaging uneven measurements by time with uneven numbers of measurements In your first request for help you said, "How do I average the measurements by every 30 minutes?" With 25000 readings over three days, it looks as if you are getting readings just about every second. Okay, why don't you use the first reading as your initial weight, w0. Then subtract each succeeding reading from that to obtain the amount of feed dispensed. Now plot that value every 30 minutes. If you are interested in the variation of feed dispensed over a half hour interval, that can be easily obtained by accummulating those half-hour readings. -- Clint Bowman INTERNET: cl...@ecy.wa.gov Air Quality Modeler INTERNET: cl...@math.utah.edu Department of Ecology VOICE: (360) 407-6815 PO Box 47600 FAX: (360) 407-7534 Olympia, WA 98504-7600 USPS: PO Box 47600, Olympia, WA 98504-7600 Parcels: 300 Desmond Drive, Lacey, WA 98503-1274 On Thu, 5 May 2011, Schatzi wrote: > I do not want smoothing as the data should have jumps (it is weight left in > feeding bunker). I was thinking of maybe using a histogram-like function and > then averaging that. Not sure if this is possible. > > ----- > In theory, practice and theory are the same. In practice, they are not - > Albert Einstein > -- > View this message in context: > http://r.789695.n4.nabble.com/Averaging-uneven-measurements-by-time-with-uneven-numbers-of-measurements-tp3499337p3499386.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. > ______________________________________________ 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.
