> Am > I right in thinking that this *should* also remove the -99s (NA > values)? Because at present, the lower end ot the file looks like this: Judging from your output, the -99's haven't been converted to NA's - you can fix this (and the 88s) by doing: PopDens[PopDens == -99] <- NA PopDens[PopDens == 88] <- NA Hadley -- http://had.co.nz/