I got bitten badly when a variable I created for the purpose of recording an old set of names changed when I didn't think I was going near it.
I'm not sure if this is a desired behaviour, or documented, or warned about. I read the data.table intro and the FAQ, and also ?setnames. Ben Bolker created a minimal reproducible example: library(data.table) DT = data.table(x=rep(c("a","b","c"),each=3), y=c(1,3,6), v=1:9) names(DT) ## [1] "x" "y" "v" oldnames <- names(DT) print(oldnames) ## [1] "x" "y" "v" setnames(DT, LETTERS[1:3]) print(oldnames) ## [1] "A" "B" "C" -- McMaster University Department of Biology http://lalashan.mcmaster.ca/theobio/DushoffLab/index.php/Main_Page https://twitter.com/jd_mathbio ______________________________________________ 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.