If I understand, try this: with(myData, factor(cumsum(evid), labels = which(evid == 1)))
On Thu, Jul 3, 2008 at 3:19 PM, Jim Price <[EMAIL PROTECTED]> wrote: > > All, > > I am constructing a pharmacokinetic dataset and have hit a snag. The > dataset > can be demonstrated in the following way: > > > > myData <- data.frame( > evid = c(1, 0, 0, 0, 1, 0, 1, 1, 1, 0), > time = 1:10, > last.dose.time = c(1, 1, 1, 1, 5, 5, 7, 8, 9, 9) > ) > > > The evid field is an indicator variable for whether the associated > observation is a dosing record (when it takes value 1) or an observation > (where it takes value 0). The time field is a date-time record for the > associated dose / observation event. I'm trying to calculate the time since > the last dose for each observation event - to support that, the data I'd > like to end up with is contained in last.dose.time, which gives the time at > which the last dosing event occured. > > The problem is in calculating the last.dose.time field; this is the first > time I've done this particular kind of data manipulation in R and I just > can't get my head around the code to solve it. > > I've been eyeballing rle and I think there may be a solution hiding in > there > somewhere, but I'm still failing to progress. Any help would be > appreciated! > > > Thanks in advance, > > Jim Price > Cardiome Pharma. Corp. > > -- > View this message in context: > http://www.nabble.com/Remembering-the-last-time-an-event-occurred-within-a-dataframe-tp18265464p18265464.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. > -- Henrique Dallazuanna Curitiba-Paraná-Brasil 25° 25' 40" S 49° 16' 22" O [[alternative HTML version deleted]]
______________________________________________ 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.
