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.
