Hi Robert, how about this (assuming your data.frame is ordered by date): tmp<-read.table(textConnection(" date y 1 2010-09-27 1356 2 2010-10-04 1968 3 2010-10-11 2602 4 2010-10-17 3116 5 2010-10-24 3496 6 2010-10-31 3958"),header=T,colClasses=c(date="Date")) tmp[max(which(tmp$date<as.Date("2010-10-06"))),"y"]
hth. Am 19.07.2012 09:42, schrieb Robert Latest: > Hello all, > > I have a dataframe that looks like this: > > head(df) > date y > 1 2010-09-27 1356 > 2 2010-10-04 1968 > 3 2010-10-11 2602 > 4 2010-10-17 3116 > 5 2010-10-24 3496 > 6 2010-10-31 3958 > > I need a function that, given any date, returns the y value > corresponding to the given date or the last day before the given date. > > Example: > > Input: as.Date("2010-10-06"). Output: 1968 (because the last value is > from 2010-10-04) > > I've been tinkering with this for an hour now, without success. I > think the solution is either surprisingly complicated or surprisingly > simple. > > Thanks, > robert > > ______________________________________________ > 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. > -- Eik Vettorazzi Department of Medical Biometry and Epidemiology University Medical Center Hamburg-Eppendorf Martinistr. 52 20246 Hamburg T ++49/40/7410-58243 F ++49/40/7410-57790 -- Pflichtangaben gemäß Gesetz über elektronische Handelsregister und Genossenschaftsregister sowie das Unternehmensregister (EHUG): Universitätsklinikum Hamburg-Eppendorf; Körperschaft des öffentlichen Rechts; Gerichtsstand: Hamburg Vorstandsmitglieder: Prof. Dr. Guido Sauter (Vertreter des Vorsitzenden), Dr. Alexander Kirstein, Joachim Prölß, Prof. Dr. Dr. Uwe Koch-Gromus ______________________________________________ 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.