Thanks for your answer! There is one thing I could not find in aggregate():
I want to have it a sum for each group of 2008,2009 and 2010. In aggregate() I can sum all the rows that have a rowname 2008, all the rows that have a rowname 2009 and all the rows that have a rowname 2010. But I want to have it summed separately each time a new group starts, so not like this: 2008 24 20 16 2009 19 12 17 2010 16 19 13 but like this: 2008 15 12 10 2009 9 3 7 2010 10 14 10 2008 9 8 6 2009 10 9 10 2010 6 5 3 -- View this message in context: http://r.789695.n4.nabble.com/Summing-rows-by-years-each-time-separately-tp4276428p4278550.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.
