On 2 June 2017 at 15:56, Romain Francois wrote: | Can you prepare a reprex ? Seconded. Minimally reproducible example or your post does not exist. https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example/ Dirk -- http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org