Duncan, Thanks you - your deparse(substitute(...)) work - fantastic. But, when I pass in multiple arguments: f(z[,1],z[,2]) I only show first argument, rest shows up as NULL -- View this message in context: http://n4.nabble.com/colname-of-arguments-tp1588146p1588872.html Sent from the R help mailing list archive at Nabble.com.