Working code would help. I would probably use 'lapply' since it appears that you want to return a variable number of items for each condition.
On Tue, Jul 8, 2008 at 2:23 PM, hesicaia <[EMAIL PROTECTED]> wrote: > > Hello, > The quick version of my question is how can I extract a matrix instead of > a vector using tapply()? I would like to be able to access both the results > of tapply() and also the index variables. > > In case further explanation would help: I am analyzing a large (3million > rows x 9 columns) spatial/temporal dataset and am attempting to calculate > the number of unique years containing any data within each geographic area > (10 degree cells in this case). I can do this, but I also want to extract a > subset vector of the index variable (area). > > My script to calculate the number of unique years containing any data for > each area is: > x<-tapply(years, area, function(x) length(unique(x))) > > Now, I want to extract the vector of areas where the number of unique years > containing any data is >20, but tapply() only returns a vector of unique > years and I was a matrix. > > I could use a looping function to do this, but tapply() is much faster with > large datasets and so I would like to use it if possible. > > Any help is appreciated. > Thanks. > -- > View this message in context: > http://www.nabble.com/extracting-index-list-when-using-tapply%28%29-tp18345794p18345794.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. > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? ______________________________________________ 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.
