It depends what would you like to get at the end. Perhaps you don't necessary need this type of numbering. For instance, if you'd like to calculate daily average.
london$id <- as.Date(london$id) For sum by day you could use, let's say, this aggregate(words~id,london,FUN=sum) If you really want what you've asked: london$one=1 u=unique(london$id) z=aggregate(one~id,london,FUN=sum) london$day=rep(seq(along.with=z$one),z$one) Mikhail > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Michela Ferron > Sent: Monday, February 14, 2011 11:09 AM > To: r-help@r-project.org > Subject: [R] How to group data by day > > Hi everybody, > > I'm a beginner in R and I'm having a hard time grouping my data by day. > The data are in this format: > > id; words > 2005-07-07T09:59:56Z; 35 > 2005-07-07T10:01:39Z; 13 > 2005-07-08T10:02:22Z; 1 > 2005-07-09T10:03:16Z; 23 > 2005-07-10T10:04:23Z; 39 > 2005-07-10T10:04:39Z; 15 > > I've transformed the date strings in dates with the function: > london$id <- transform(london$id, as.Date(london$id, format="%Y-%m- > %d%T%H:%M:%S%Z")) > and it seems to work. > > Now I would like to add a new "day" variable to group data by day, like > this: > > id; words; day > 2005-07-07T09:59:56Z; 35; 1 > 2005-07-07T10:01:39Z; 13; 1 > 2005-07-08T10:02:22Z; 1; 2 > 2005-07-09T10:03:16Z; 23; 3 > 2005-07-10T10:04:23Z; 39; 4 > 2005-07-10T10:04:39Z; 15; 4 > > How can I do that? > > Many thanks! > > Michela > > ______________________________________________ > 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.
