I have found that factor vectors are shy beasts. Consider:
> empty <- factor(levels=c("eins", "zwei")) > value <- factor("eins", levels=c("eins", "zwei")) > c(empty, value) [1] 1 > empty[1] <- value > empty [1] eins Levels: eins zwei > I could not exactly predict this behaviour, but ?c says: The output type is determined from the highest type of the components in the hierarchy NULL < raw < logical < integer < real < complex < character < list < expression. As factor is a class (of the whole vector) and not a type (of a single element), c does not seem to preserve the object information, i.e. there does not seem to be a c.factor, correct? -- Johannes Hüsing There is something fascinating about science. One gets such wholesale returns of conjecture mailto:[EMAIL PROTECTED] from such a trifling investment of fact. http://derwisch.wikidot.com (Mark Twain, "Life on the Mississippi") ______________________________________________ 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.