Next time if dd is your data frame display dput(dd) so we know exactly what you have.
>From your output I guessed it was numeric but the behavior of the 0/1 column that you describe is consistent with it being a factor rather than numeric. Try dd$of <- as.numeric(levels(dd$of)[dd$of]) or equivalently dd$of <- as.numeric(as.character(dd$of)) to make them numeric first. ave() takes each group of rows of dd$of that have the same dd$Id and applies FUN separately to it forming a vector like dd$Id but with the output of each application of FUN replacing the input in that vector. On Thu, Oct 22, 2009 at 2:36 AM, clion <birt...@hotmail.com> wrote: > > thanks, it works! well, now it shows 1s instead of 0s and 2s instead of 1s, > which fine with me...but could you explain me what this function actually > does? > > > Gabor Grothendieck wrote: >> >> Iff dd is your data frame then: >> >> dd$prev <- ave(dd$of, dd$Id, FUN = function(x) c(NA, head(x, -1))) >> >> >> On Wed, Oct 21, 2009 at 2:55 AM, clion <birt...@hotmail.com> wrote: >>> >>> Dear Rlers, >>> in the following dataset I would like to insert a new column that refers >>> to >>> the data of the previous row. >>> My question is whether the probability of a female (Id) changes if she >>> had >>> given birth to a pup in the previous year. So my dataframe consists of >>> the >>> column Id, year (2003-2007 for each Id) and offspring (=of; 1-0): >>> Id year of >>> 1 2003 1 >>> 1 2004 0 >>> 1 2005 1 >>> 1 2006 1 >>> 1 2007 0 with 1= female (Id) gave birth to offspring (same year) >>> 2 2003 0 and 0 = female didn't pup >>> 2 2004 1 >>> 2 2005 1 >>> 2 2006 0 >>> 2 2007 1 >>> 3 2003 1 >>> 3 2004 1 >>> 3 2005 1 >>> 3 2006 0 >>> 3 2007 0 >>> Now I want to add the column "offspring in the previous year - >>> yes/no(1-0)" >>> the output now should look like this: >>> >>> Id year of of_inPreviousYear >>> 1 2003 1 NA >>> 1 2004 0 1 >>> 1 2005 1 0 >>> 1 2006 1 1 >>> 1 2007 0 1 >>> 2 2003 0 NA >>> 2 2004 1 0 >>> 2 2005 1 1 >>> 2 2006 0 1 >>> 2 2007 1 0 >>> 3 2003 1 NA >>> 3 2004 1 1 >>> 3 2005 1 1 >>> 3 2006 0 1 >>> 3 2007 0 0 >>> >>> any idea how I could program that? >>> >>> thanks a lot, >>> clion >>> -- >>> View this message in context: >>> http://www.nabble.com/referring-to-data-of-previous-rows-tp25987364p25987364.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. >> >> > > -- > View this message in context: > http://www.nabble.com/referring-to-data-of-previous-rows-tp25987364p26004769.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.
