Hi RajPatil It seems that you are using an old version of mlxLibrary. You need to install mlxLibrary 1.1.0 from the Lixoft website http://download.lixoft.com/?software=mlxlibrary Marc -- View this message in context: http://r.789695.n4.nabble.com/Error-in-running-pkmodel-function-in-mlxR-package-tp4702110p4702745.html Sent from the R help mailing list archive at Nabble.com.