Dear all, pmin/pmax used to work with ordered factors but fail now since this summer when those functions have tried to handle more cases. A simple way to trigger the issue is: > min(ordered(c(1,5,6))) [1] 1 Levels: 1 < 5 < 6 > pmin(ordered(c(1,5,6)), ordered(c(1,5,6))) Error in `mostattributes<-`(`*tmp*`, value = attributes(elts[[1L]])) : adding class "factor" to an invalid object A simple fix is to explicitly test for the ordered class and use the internal method in that case as proposed in the attached patch. Yours, Erwan -------------- next part -------------- A non-text attachment was scrubbed... Name: patch.diff Type: text/x-patch Size: 1016 bytes Desc: not available URL: <https://stat.ethz.ch/pipermail/r-devel/attachments/20161130/71dc22b6/attachment.bin>