Hi I have a data.frame, two columns, 12304 rows. Both columns are factors. I want to do an equivalent of an SQL "group by" statement, and count the number of rows in the data frame for each unique value of the second column.
I have: countl <- by(mapped, mapped$col2, nrow) Now, mapped$col2 has 10588 levels, so this statement takes a really long time to run. Is there a more efficient way of doing this in R? Thanks Mick ______________________________________________ R-help@stat.math.ethz.ch 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.
