Uwe Ligges <ligges at statistik.uni-dortmund.de> writes: > These are all dangerous, hence use the "safe" ways: > > sapply(a, is.null) > sapply(a, identical, "NULL") > sapply(a, is.na) > sapply(a, identical, "NA") Point taken, but is the behavior of as.character correct? as.character(list(NULL)) as.character(NULL) + seth