Thanks to all who responded. In particular, thanks to Jim Lemon who pointed out that just because
mode(MSA) returned ''numeric', doesn't mean MSA isn't a factor. It turned out, indeed, to be a factor. Peter ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
