Hello Rick, This may be way to late but I had the same error and solved it just removing the ?na.action=? argument. Since I had removed the NAs beforehand it did not affect my results. Best, Lau Laureano A. Gherardi PhD Sala Lab <http://sala.lab.asu.edu/people/> LSA 217A School of Life Sciences <https://sols.asu.edu/> Arizona State University PO Box 874501 Tempe, AZ, 85287-4501 1+(480) 727-3726 My Research Gate <https://www.researchgate.net/profile/Laureano_Gherardi/?ev=hdr_xprf> My Google Scholar <https://scholar.google.com/citations?user=GH72YJ8AAAAJ&hl=en> [[alternative HTML version deleted]]