On Mon, Sep 17, 2012 at 11:03 AM, Tagmarie <ramga...@gmx.net> wrote: > Even though I work with R since a year or so I still struggle with simple > problems. I hope someone can help me with this. Been trying for days and am > a little frustrated now. > > I have a data frame somewhat like the one bellow: > > dattrial<-data.frame(a=c(1,NA,rnorm(4,10)), Week=c(3,3,3,4,4,4)) > > I want to know how many NAs I have in week 3 and in week 4. > >
Thanks for the reproducible example: there are many ways to do this (aggregate, tapply, ave, etc.) but they are all based on the paradigm of: break up your data by "Week" --> apply the function "function(x) sum(is.na(x))" --> recombine. (See, inter alia, the JSS paper on the plyr package) I'm not at a computer with R right now so this is a little untested, but one way might be: with(dattrial, tapply(a, Week, function(x) sum(is.na(x)))) Cheers, Michael > > -- > View this message in context: > http://r.789695.n4.nabble.com/count-NAs-per-week-tp4643351.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.
