dat <- structure(list(date = structure(c(14879, 14886, 14893, 14899, 14906, 14913), class = "Date"), y = c(1356L, 1968L, 2602L, 3116L, 3496L, 3958L)), .Names = c("date", "y"), row.names = c("1", "2", "3", "4", "5", "6"), class = "data.frame")
x <- as.Date( "2010-10-06" ) getY <- function( x ) { dat[ dat$date <= x, 2][ length( dat[ dat$date < x, 2] ) ] } getY( x ) [1] 1968 getY( as.Date( "2010-10-17" ) ) [1] 2602 Is that what you want? Rgds, Rainer -------- Original-Nachricht -------- > Datum: Thu, 19 Jul 2012 09:42:05 +0200 > Von: Robert Latest <boblat...@gmail.com> > An: > Betreff: [R] Finding the last value before a certain date > 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. -- ------- Gentoo Linux with KDE ______________________________________________ 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.