Aggregate does the right thing with column names when passing it numerical coordinates. Given a dataframe like this:
Nuclei Positive Nuclei Slide 1 133 96 A1 2 96 70 A1 3 62 52 A2 4 60 50 A2 I can call 'aggregate' like this: > aggregate(example[1], by=example[3], sum) Slide Nuclei 1 A1 229 2 A2 122 But that means I have to keep track of which column is which number. If I try it the easy way, it doesn't keep track of column names and it forces me to coerce the 'by' to a list. > aggregate(example$Nuclei, by=list(example$Slide), sum) Group.1 x 1 A1 229 2 A2 122 Is there a better way to do this? Thanks -Ed ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
