Hi, The man page for sort.list says: Method ?"radix"? is only implemented for integer ?x? with a range of less than 100,000. but actually: > sort.list(c(4L, -5L), method="radix") Error in sort.list(c(4L, -5L), method = "radix") : negative value in 'x' Implementation bug or documentation bug? Here is an old post more or less related to this: https://stat.ethz.ch/pipermail/r-devel/2011-February/060000.html Thanks, H. -- Herv? Pag?s Program in Computational Biology Division of Public Health Sciences Fred Hutchinson Cancer Research Center 1100 Fairview Ave. N, M1-B514 P.O. Box 19024 Seattle, WA 98109-1024 E-mail: hpages at fhcrc.org Phone: (206) 667-5791 Fax: (206) 667-1319